The Largest Reservoirs in the United States

Man-made lakes behind America’s great dams, ranked by surface area.

The great dams of the 20th century turned rivers like the Colorado, Missouri and Columbia into chains of man-made lakes. Ranked here by full-pool surface area — in recent drought years Lake Mead and Lake Powell have covered far less.

#	Place	Area (sq mi)
1	Lake Oahe A 231-mile Missouri River reservoir across the Dakotas	579 sq mi 1,500 km²
2	Lake Sakakawea The Garrison Dam reservoir on the Missouri River in North Dakota	479 sq mi 1,240 km²
3	Lake Powell Glen Canyon Dam's reservoir on the Colorado River in Utah and Arizona	252 sq mi 653 km²
4	Lake Mead Hoover Dam's reservoir on the Colorado River, now at record lows	247 sq mi 640 km²
5	Grand Coulee Dam The largest power plant in the United States, on the Columbia River	125 sq mi 324 km²
6	Shasta Lake California's largest reservoir, behind Shasta Dam on the Sacramento River	47 sq mi 121 km²

Place

Area (sq mi)

Lake Oahe
A 231-mile Missouri River reservoir across the Dakotas

579 sq mi
1,500 km²

Lake Sakakawea
The Garrison Dam reservoir on the Missouri River in North Dakota

479 sq mi
1,240 km²

Lake Powell
Glen Canyon Dam's reservoir on the Colorado River in Utah and Arizona

252 sq mi
653 km²

Lake Mead
Hoover Dam's reservoir on the Colorado River, now at record lows

247 sq mi
640 km²

Grand Coulee Dam
The largest power plant in the United States, on the Columbia River

125 sq mi
324 km²

Shasta Lake
California's largest reservoir, behind Shasta Dam on the Sacramento River

47 sq mi
121 km²

Figures are drawn from standard government and reference sources and shown in both imperial and metric units. See each entry for full details and citations. Browse all guides or open the explore map.