Paleo-Indians of the Clovis culture and Folsom culture inhabited the Colorado Plateau, marking the earliest documented human presence connected to the Colorado River region.
Cliff Palace, Mesa_Verde_National_Park
During the Desert Archaic period, populations increased in the region; evidence of agriculture, masonry dwellings, and petroglyphs later becomes more prominent.
The Fremont culture period is associated with early evidence of agriculture, masonry dwellings, and petroglyphs across parts of the Colorado Plateau.
The Hohokam were present in the modern Phoenix area and later developed extensive irrigation canals using the Salt River.
The Hohokam experienced significant growth as they constructed a large system of irrigation canals, supporting substantial populations in central Arizona.
The Ancient Puebloan culture became established in the Four Corners region, with extensive evidence of habitation in areas near the wider Colorado Plateau.
The Navajo (Diné) began migrating into the Colorado River Basin, later expanding their influence across much of the Colorado Plateau.
Navajo woman and child, photographed by Ansel_Adams, c. 1944
Francisco de Ulloa may have been the first European to see the Colorado River, sailing to the head of the Gulf of California.
La conquista del Colorado (2017), by Augusto_Ferrer-Dalmau, depicts Francisco_Vázquez_de_Coronado's 1540–1542 expedition. García_López_de_Cárdenas can be seen overlooking the Grand_Canyon.
García López de Cárdenas became the first European to see the Grand Canyon, during Francisco Vásquez de Coronado's expedition.
Melchior Díaz explored the Colorado River delta and named it Rio del Tizon ("fire brand river").
The name Rio Colorado appeared on the map "Paso por Tierra a la California" published by missionary Eusebio Kino.
Juan Bautista de Anza reached Yuma Crossing, established relations with the Quechan, and opened the Anza Trail.
The Dominguez–Escalante expedition reached the Colorado River near the Dolores River, and later forded the river at Crossing of the Fathers (now submerged in Lake Powell).
Spanish attempts to control the Yuma Crossing contributed to the 1781 Yuma revolt; Spanish settlements along the lower Colorado River were abandoned afterward.
William H. Ashley attempted unsuccessfully to navigate from the Green River to the Colorado River’s mouth.
Jedediah Smith reached the lower Colorado River and explored upstream as far as Black Canyon.
John C. Frémont explored the Great Basin and concluded that no Buenaventura River flowed west to California.
George A. Johnson, piloting the General Jesup, reached Pyramid Canyon upstream of Fort Yuma.
Gold was discovered on the Gila River east of Yuma, and later along the Colorado near El Dorado Canyon, Nevada and La Paz, Arizona.
U.S. Army expeditions culminated in the 1859 Battle of the Colorado River, concluding the Mohave War.
The Blue River gold strike helped spur settlement in the Upper Basin and led to the founding of Breckenridge, Colorado.
Joseph C. Ives surveyed the lower Colorado River and described its rapidly shifting channels and river features.
General James Henry Carleton enlisted Kit Carson to lead a campaign against the Navajo, initiating forced removals that became known as the Long Walk of the Navajo.
A federally funded irrigation canal was built on the Colorado River Indian Reservation, described as the first federally funded irrigation project in the U.S.
The Treaty of Bosque Redondo established the Navajo Nation, allowing Navajo people to return to the Four Corners region.
John Wesley Powell led the Powell Geographic Expedition of 1869, the first party of non-natives to travel the length of the Grand Canyon and successfully boat from the upper Green River to the lower Colorado.
Route of Powell's first expedition, 1869.
Powell led a second expedition with U.S. government backing and continued geographic and botanical surveys across the region into the 1890s.
Boats of John_Wesley_Powell's second Colorado River expedition in Marble_Canyon, 1872.
The Brunot Agreement was signed, reducing Ute land rights and accelerating mineral prospecting and settlement in western Colorado.
John D. Lee, associated with the establishment of Lee's Ferry, was tried and executed; the ferry continued operating as a key crossing until 1928.
Historic photograph of the cable ferry at Lee's_Ferry, prior to construction of the Navajo_Bridge.
Mormon settlers undertook the San Juan Expedition, creating the Hole in the Rock Trail to cross the river in Glen Canyon and establish the community of Bluff, Utah.
The Army drove out remaining pockets of Ute resistance on Colorado’s Western Slope (1881), and Grand Junction, Colorado was incorporated (1882).
The Denver and Rio Grande Western Railroad reached Grand Junction (1883) and completed a spur up the Colorado to Glenwood Springs (1887), supporting mining and settlement.
Robert Brewster Stanton led a Grand Canyon river expedition to survey a route for a proposed railroad through the canyon, which was never built.
The Grand Ditch—one of the earliest diversions at the river’s headwaters—was completed, moving water across the Continental Divide to eastern Colorado.
The Grand_Ditch, one of the earliest water diversions of the Colorado River, is still in use today.
The California Development Company began pursuing irrigation of the Imperial Valley via the Alamo Canal, diverting Colorado River water toward the Salton Sink.
Irrigation via the Alamo Canal helped spur settlement in the Imperial Valley, with thousands of residents and over 100,000 acres of farmland developed.
Flooding destroyed Alamo Canal intake gates (1905), causing uncontrolled diversion that flooded the Imperial Valley and created the modern Salton Sea; after multiple attempts, the breach was blocked and the river restored to its course (1907).
The Denver and Salt Lake Railway was incorporated to seek a more direct rail link between Denver and Salt Lake City; it later faced financial limitations before reaching Utah.
President Warren G. Harding signed House Joint Resolution 32, renaming the upper river previously known as the Grand River to the Colorado River.
Six U.S. states signed the Colorado River Compact, allocating 7.5 million acre-feet per year each to the Upper and Lower Basins and forming the foundation for later water governance.
The Navajo Bridge was completed near Lee's Ferry, rendering the ferry crossing largely obsolete.
Congress authorized the Boulder Canyon Project to build a major dam in Black Canyon.
Hoover_Dam under construction, 1934
The D&RGW completed the “Dotsero Cutoff,” helping finalize a more direct Denver–Salt Lake rail connection via the Colorado River corridor.
Initial closure of Hoover Dam began moderating lower Colorado River flows, reducing natural seasonal variability below the dam.
Hoover Dam was completed, forming Lake Mead and providing flood control, irrigation storage, sediment capture, and hydroelectric generation.
Hoover_Dam releasing water in 1998
Las Vegas tapped a pipeline into Lake Mead, supporting municipal growth dependent on Colorado River infrastructure.