The expedition produced the first detailed climate records of the West

Clark’s maps provided the first detailed record of the American West

Covering over 8,000 miles, William Clark’s maps charted rivers, mountains, and tribal territories with remarkable accuracy. Equipped with sextants, compasses, telescopes, and more, Clark became an expert at surveying—requiring extensive celestial and topographical observations each day.

Explore Lewis and Clark's 8,000-mile journey in Google Earth.

Lewis and Clark’s journey became a blueprint for future exploration

Combining science, diplomacy, and logistics, the Corps of Discovery created a model for later expeditions—from charting the Arctic to NASA’s space missions.

The expedition documented 240 plant species, 178 new to western science

Lewis and Clark’s botanical records introduced species to Americans like bitterroot, ponderosa pine, and Oregon grape—plants unknown to western science at the time. See a selection of these species in this image gallery.

The Lewis and Clark expedition lasted over two years

The Corps of Discovery departed St. Louis in May 1804 and returned in September 1806, covering more than 8,000 miles by boat, horseback, and on foot. See a timeline of the journey’s key events.

Jefferson sent Lewis and Clark to map, trade, and secure the West

Beyond seeking a water route to the Pacific, Jefferson tasked the Corps of Discovery with mapping the new Louisiana Territory, cataloging its resources, and establishing trade with Native nations.

The Corps of Discovery braved wildlife, weather, and near-starvation

Along their 8,000-mile trek through territory populated by tribes suspicious of their intentions, Lewis and Clark’s party faced many dangers—including grizzly bear attacks, freezing winters, treacherous river crossings, and periods of near-starvation. Watch a 30-minute elaboration of their heroic efforts here.

Lewis and Clark identified 122 animal species new to science.

The Lewis and Clark Expedition brought along an estimated 120 gallons of whiskey and still ran out of alcohol halfway through the journey.

Discover the 'American Serengeti' Lewis and Clark first recorded

This podcast traces the 19th-century exploration of the Great Plains' biodiversity—beginning with Lewis and Clark's wildlife cataloging and continuing through a century of documenting the Natural West's remarkable species and landscapes.

Jefferson’s Lewis and Clark expedition joined the centuries-long hunt for Northwest Passage

For centuries, leaders pursued a direct seafaring trade route from Europe to Asia. Jefferson joined this quest by sending Lewis and Clark west, though they confirmed no such practical interior route existed across the continent.

The Lewis and Clark expedition purchased more than 260 separate items to supply their journey.

Lewis and Clark encountered more than 70 Native tribes during their journey

The Corps of Discovery’s diplomacy ranged from peaceful trade and vital aid from tribes like the Shoshone and Nez Perce to tense standoffs, most notably with the Teton Sioux, who nearly brought the expedition to a halt.

Native voices share their histories along the Lewis and Clark National Historic Trail

Tribal historians recount their peoples' histories and perspectives on the Lewis and Clark expedition, offering an Indigenous narrative of the lands, encounters, and legacies that shaped the journey.

William Clark negotiated one-tenth of all ratified treaties between Native Americans and the US.

A free archive of firsthand historical documents from explorers of America

Maintained by the Wisconsin Historical Society, the American Journeys collection contains more than 18,000 pages of primary source documents—journals, letters, maps, and accounts written between roughly 1000 CE and the early 1800s. These include eyewitness records of the Norse arrival in North America, Spanish conquistador expeditions, and the Lewis and Clark journey. Browse this list of highlights where pages from the original texts are specified (clicking a link opens a PDF).

Jefferson omitted a plan to go beyond the Louisiana Territory in his funding request

In January of 1803, the president sought $2,500 to fund the expedition (though it likely cost closer to $50,000). The ostensible rationale for the journey was to explore the newly purchased territory, but Jefferson did not mention he wanted Lewis and Clark to go beyond the newly acquired territory for several reasons.

The weather time machine

A fun interactive on how old ships’ logs are giving scientists new insights into the past and future of the Earth’s changing climate (w/maps and pictures).

The Lewis and Clark Expedition unexpectedly ran into Sacagawea's long-lost family in the Rocky Mountains.

The expedition included Clark’s enslaved servant, York

York, Clark’s enslaved servant, played a full role in the expedition—hunting, scouting, and aiding diplomacy with Native nations who were fascinated by his appearance. Despite his contributions, York remained enslaved for some time after the journey, though its uncertain if he remained so for the rest of his life. Explore every member of the Corps of Discovery here.

Meriwether Lewis grew up in the same neighborhood as Jefferson

Hailing from Jefferson’s Albemarle County neighborhood in Virginia, Lewis was a trusted aide and former Army officer. After leading the Corps of Discovery, he became Louisiana Territory governor in 1806, dying three years later under mysterious circumstances.

The first women to run the Colorado River discovered four plant species

Over 45 days and 660 miles, Elzada Clover and Lois Jotter identified more than 50 species in what was the first botanical survey of the region. Expected to help navigate boats and cook for the crew during the day, their work was confined to before dawn and after dusk.

Climate data is monitored globally using tools from satellites to backyard gauges

Scientists use satellites, balloons, ocean buoys, and land-based instruments to track climate variables like temperature, precipitation, and wind. These tools gather data from deep ocean waters to the upper atmosphere.

A map of extreme weather events and their links to climate change

To track how the evidence on this fast-moving topic is stacking up, Carbon Brief has mapped every extreme-weather attribution study published to date. Read more about the findings from the comprehensive analysis.

Climatologists use past data and advanced models to forecast future climate trends

Unlike meteorology, which focuses on weather forecasting over several days, climatology identifies trends in data over periods of 30 or more years. This data can go back millions of years and help refine models to forecast centuries into the future.

The Corps traded gifts with many native tribes as a sign of goodwill

They offered peace medals, beads, cloth, and mirrors, while receiving food, horses, furs, and guidance that helped them navigate and survive the western wilderness. This image collection showcases items the expedition collected.

Snowfall records from every county in the US

Discover the one-day snowfall records of every county in the US in this comprehensive map. Data from the National Oceanic and Atmospheric Administration captures inches of snowfall and the year it fell the most in each county. See the contrasts between the inches of snowfall in warm southern American states and the cooler East Coast.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Meteorological v. astronomical seasons, explained

Meteorologists and climatologists define seasons differently from “regular” or astronomical spring, summer, fall, and winter. Traditional seasons reflect the movement of celestial objects, known as the astronomical seasons; meteorologists mark seasonal change based on temperature averages.

Scientists use climate proxies—physical, chemical, and biological materials preserved in sediments, ice, and fossils—to infer historical climate data and determine past climate patterns.

View the 55 ECVs used to describe Earth's atmospheric conditions

Essential climate variables include physical, chemical, and biological variables that meaningfully contribute to Earth's climate and how it changes with time. Many of these variables influence one another through feedback mechanisms across Earth's atmosphere, hydrosphere, cryosphere, biosphere, and geosphere.

Lewis brought his loyal Newfoundland dog on the expedition

Meriwether Lewis was accompanied by his dog, Seaman, a Newfoundland who traveled the entire journey—helping hunt, guarding camp, and even rescuing supplies from a river.

Explore a series of interdisciplinary explainers on climate science

From animations on the quantum mechanics of greenhouse gases to a photo essay on how scientists acquire climate data, this collection provides detailed explorations of how different branches of science have contributed to our understanding of climatology.

The Viking landers were the first spacecraft to conduct experiments on Mars

NASA’s Viking 1 and 2 missions tested soils for signs of life, captured images, and studied the Martian atmosphere, revealing evidence of ancient water flow, volcanic soil, and a thin carbon dioxide atmosphere.

In the 1940s, pilots flew into thunderstorms to learn about their formation and properties as part of the Thunderstorm Project, the first multiagency meteorological study mandated and funded by Congress.

Discover trends in Earth's climate system: What are indicators of climate change?

A comprehensive deep dive tracking components of the climate system over time, such as temperature, sea level, sea ice amounts, ocean heat, greenhouse gases, and more (w/charts and graphs).

This year's first leaf and first bloom in the US, mapped

Spring tends to arrive within a range of dates in the contiguous US. See a map illustrating the most recent year's first leaf and first bloom in relation to historical averages to see how early or late the season arrived.

View depictions of world maps throughout history

The first map to use latitude and longitude positions was created by Ptolemy in 150 CE, over 700 years after the oldest known world map, the Imago Mundi, was made with a Babylonian clay tablet. The Spanish crown created a secret master map from hundreds of sailors’ reports.

In 2025, UK scientists began studying climate data from a 1.5-million-year-old ice core

The Antarctica sample will be melted and analyzed in Cambridge to learn about prehistoric environmental conditions. Researchers hope the ice core reveals how Earth's glacial cycles shifted dramatically around 800,000 years ago.

Explore an interactive global weather map, with overlays depicting real-time data on temperature, precipitation, wind, humidity, and pressure, which enable the tracking and monitoring of extreme weather events.

Yellowstone was the world's first national park

Before it was designated as such, it was home to 27 Indigenous tribes, including the Blackfeet, Crow, and Nez Perce. European trappers and traders traveling west were entranced by the area’s stunning beauty and natural resources, fueling a push for the government to preserve the land for future generations.

Explore how temperatures compare to historical averages in cities worldwide with this interactive global monitor.

Railroads and long-distance communication led to the development of time zones, with Greenwich established as the prime meridian—the longitude of 0 degrees—due to British advancements in star mapping and navigation.

A medieval warm period reshaped agriculture across parts of the world

Between 750 and 1350 CE, some regions experienced temperatures that rivaled or exceeded late-20th-century averages, likely due to shifts in El Niño–La Niña cycles. The warmer, wetter climate in Europe and northeast North America boosted agriculture, while causing droughts elsewhere.

Hear the story of the early American environmentalists who shaped the public lands we enjoy today.

The greenhouse effect was discovered by analyzing Earth's temperature

Using mathematical techniques developed to analyze heat transfer, Jean-Baptiste Joseph Fourier showed that Earth should be significantly cooler if solar radiation were the only contributor to its surface temperature. By considering that the atmosphere could amplify the sun's warming effect, he formulated what became known as the greenhouse effect.

Visualize real-time and historical atmospheric conditions from around the world

This tool provides live maps of wind, rain, thunderstorms, and other atmospheric phenomena overlayed on an interactive map of the Earth. Users can enter their location to explore local atmospheric dynamics and review historical weather conditions dating back to 1979.

Scientists can determine Earth's past environmental conditions by analyzing sediment cores—accumulated layers of mud and remains of charcoal, pollen, plants, algae, and other organic material.

George Washington was an expert in maps and cartography

Trained as a surveyor, Washington routinely studied, annotated, and drew maps throughout his life. He relied on cartography to navigate frontier lands, plan military campaigns across vast distances, and make strategic decisions on borders, settlement, and governance.

Why the Antarctic climate enabled British scientists to discover the ozone hole

In the Antarctic stratosphere, polar conditions facilitate the formation of polar stratospheric clouds, which allow chlorine compounds from chlorofluorocarbons to accumulate. In 1985, British Antarctic Survey scientists detected massive springtime losses over Antarctica, as accumulated compounds destroyed significant amounts of ozone once sunlight returned.