Colorado River
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50 free Colorado River trivia questions with answers — geography quiz, new questions added Oct 2026.
The Colorado River is far from the longest river in the United States, yet few rivers anywhere work as hard. It carved the Grand Canyon, it turns the turbines of Hoover Dam, and it keeps taps running and crops growing across the desert Southwest. This quiz turns the river's best fun facts into questions. They cover where the water comes from and where it ends up, the dams and reservoirs along the way, the explorers who first ran its rapids, the animals that depend on it, and the long arguments over who gets to use it. A few surprises from film, sport and engineering are mixed in. The questions suit anyone curious about the Southwest: students working on a geography project, travellers planning a trip through canyon country, and trivia fans who like a fact worth repeating at dinner. Every answer comes with a short explanation.
30 of 50 questions with answers and explanations. Play the quiz
Q 01What has the Colorado River rarely done since the 1960s because farms and cities take nearly all its water?
Reach the sea
Dams and diversions have dried up the river's last 100 miles, so it has failed to reach the sea in most years since the 1960s.
Q 02The Colorado River takes its Spanish name from which feature of its water?
Its reddish color
Its reddish color came from the mud the river once carried in vast amounts; the name Rio Colorado first appeared on a missionary's map in 1701.
Q 03Which one-armed Civil War veteran led the first boat expedition through the Grand Canyon in 1869?
John Wesley Powell
John Wesley Powell lost his right arm at the Battle of Shiloh, yet in 1869 he spent three months riding wooden rowboats through uncharted rapids.
Q 04Which European landmark was bought, shipped to Arizona and rebuilt at Lake Havasu City on the Colorado River?
London Bridge
London Bridge was bought by developer Robert McCulloch, who rebuilt its granite facing over a channel he dredged to draw tourists and home buyers to his new town.
Q 05Which California lake formed by accident when the Colorado River burst through an irrigation canal in 1905?
Salton Sea
The Salton Sea filled a dry desert basin for two years while the entire river poured in, and it is now the largest lake in California.
Q 06Which much-photographed curve of the Colorado River lies just downstream of Glen Canyon Dam near Page, Arizona?
Horseshoe Bend
Horseshoe Bend is an entrenched meander where the river swings almost full circle, 1,000 feet below a cliff-edge overlook.
Q 07Which desert city draws about 90 percent of its water from the Colorado River through intakes in Lake Mead?
Las Vegas
Las Vegas gets around 90 percent of its supply from Lake Mead and earns credits for the water it returns to the lake.
Q 08An entirely separate Colorado River, the longest wholly inside one US state, flows through which state capital?
Austin
Austin sits on the Texas Colorado, which runs from the plains near Lubbock to Matagorda Bay and never meets its western namesake.
Q 09About how deep has the Colorado River cut into the plateau at the deepest point of the Grand Canyon?
1 mile
The canyon is about 1 mile deep from rim to river, and the rocks laid bare at the bottom are up to 2 billion years old.
Q 10Which tiny marine mammal, the most endangered on Earth, lives only in the sea beside the Colorado River's delta?
Vaquita
The vaquita, whose name is Spanish for little cow, is the smallest of all cetaceans and drowns in gillnets set illegally for another fish.
Q 11The Colorado River's delta lies at the head of which long, narrow sea on the Pacific side of Mexico?
Gulf of California
The Gulf of California, also called the Sea of Cortez, would stretch far inland to the desert town of Indio if the river's silt had not walled off its northern end.
Q 12The Colorado River begins as a trickle at La Poudre Pass, on the Continental Divide inside which national park?
Rocky Mountain
Rocky Mountain National Park holds the headwaters: a wet meadow at 10,184 feet where the mighty river starts out as a tiny stream.
Q 13Which president dedicated Hoover Dam in 1935, when the job was running two years ahead of schedule?
Franklin Roosevelt
Q 21Which safety item did Hoover Dam's builders order by the thousand after workers improvised their own using tar?
Hard hats
Hard hats were ordered by the thousand after the men who dangled from the canyon walls dipped cloth hats in tar and let them harden; the factory-made kind were first called hard boiled hats.
Q 22Tunnels under the Continental Divide send Colorado River water east to which state capital for half its supply?
Denver
Denver sits on the dry side of the mountains: about 80 percent of its state's people live east of the divide, while 80 percent of the precipitation falls to the west.
Q 23From 1852 to 1909, which vessels hauled soldiers' and miners' supplies up the lower Colorado River from the sea?
Steamboats
Franklin Roosevelt dedicated the dam on September 30, 1935, and a star map set into the terrazzo floor beside it records the sky at that moment.
Q 14Which town, built in 1931 to house Hoover Dam's construction workers, still bans gambling inside its limits?
Boulder City
Boulder City began as a strict federal company town where alcohol stayed illegal until 1969, and it is one of only two places in its state that prohibit gambling.
Q 15Arizona's governor sent National Guard troops in the 1930s to halt construction of which Colorado River dam?
Parker Dam
Parker Dam was being built to feed a California aqueduct, and Arizona feared losing its water; it is also the world's deepest dam, with most of its height sunk below the riverbed.
Q 16Which state settled for the smallest share of Colorado River water because its leaders prized dam power instead?
Nevada
Nevada took just 300,000 acre-feet a year, a fraction of its neighbours' shares, because officials assumed groundwater would cover future growth.
Q 17Which tributary, longer than the upper Colorado itself, joins the Colorado in Utah's Canyonlands National Park?
Green River
The Green River is the Colorado's largest tributary, so Wyoming and Utah objected in 1921 when Congress declared the shorter branch the main stream.
Q 18The bridge beside Hoover Dam is named partly for which NFL player who was killed serving in Afghanistan?
Pat Tillman
Pat Tillman left the Arizona Cardinals to enlist in the Army; the arch that shares his name carries a highway about 890 feet above the river.
Q 19Before its dams, the Colorado River carried the second-most silt of any North American river, behind which one?
Mississippi
Only the Mississippi moved more: the Colorado once hauled up to 100 million tons of silt a year, most of which now settles in its reservoirs.
Q 20Which natural record later showed that the Colorado River was divided among states during unusually wet decades?
Tree rings
Tree rings revealed that the years used to set each share were probably the wettest in at least five centuries, so more water was promised than the river holds.
Steamboats worked the desert river for more than fifty years, beginning with a 65-foot side-wheeler named Uncle Sam, until Laguna Dam blocked the channel.
Q 24Which Arizona city at an ancient crossing of the lower Colorado River does Guinness rank as the sunniest on Earth?
Yuma
Yuma grew up where the channel narrows enough to cross, and the sun is said to shine there for about 90 percent of daylight hours.
Q 25Which giant endangered bird, released nearby in 1996, is sometimes seen on Navajo Bridge above the Colorado River?
California condor
The California condor, North America's largest land bird, disappeared from the wild in 1987 before condors were released again at cliffs near the bridge.
Q 26The heavily dammed Colorado River is often given which nickname that likens it to a great African river?
America's Nile
America's Nile suits a desert river that waters 5.5 million acres of farmland; each drop is said to be used about 17 times in a single year.
Q 27What repeatedly dammed the Colorado River in the prehistoric Grand Canyon, once to a height of 2,300 feet?
Lava flows
Lava flows from a volcanic field in northern Arizona built at least 13 natural dams, and the lake behind the highest stretched almost 500 miles upstream.
Q 28Scouts from which conquistador's hunt for the Seven Cities of Gold were the first Europeans to see the Grand Canyon?
Coronado
Coronado sent García López de Cárdenas north in 1540; his party reached the South Rim, badly underestimated the canyon's size and left disappointed, with no gold.
Q 29Which Edward Abbey novel follows eco-saboteurs whose ultimate target is Glen Canyon Dam on the Colorado River?
The Monkey Wrench Gang
The Monkey Wrench Gang, published in 1975, was so influential that monkeywrenching became a word for sabotage carried out to protect wild places.
Q 30David Brower, who called the drowning of Glen Canyon by a Colorado River dam his greatest sin, led which group?
Sierra Club
The Sierra Club under Brower stopped two dams planned for Dinosaur National Monument, but Glen Canyon's dam was enlarged in exchange, and he saw the canyon only after the decision.