<Table> <Tr> <Th_colspan="2"> Hoover Dam </Th> </Tr> <Tr> <Td_colspan="2"> Hoover Dam by Ansel Adams, 1942 </Td> </Tr> <Tr> <Th> Official name </Th> <Td> Hoover Dam </Td> </Tr> <Tr> <Th> Location </Th> <Td> Clark County, Nevada / Mohave County, Arizona, U.S. </Td> </Tr> <Tr> <Th> Purpose </Th> <Td> Power, flood control, water storage, regulation, recreation </Td> </Tr> <Tr> <Th> Status </Th> <Td> In use </Td> </Tr> <Tr> <Th> Construction began </Th> <Td> 1931 </Td> </Tr> <Tr> <Th> Opening date </Th> <Td> 1936 </Td> </Tr> <Tr> <Th> Construction cost </Th> <Td> $49 million (1931 budget) ($4.52 billion in 2016 dollars) </Td> </Tr> <Tr> <Th> Owner (s) </Th> <Td> United States Government </Td> </Tr> <Tr> <Th> Operator (s) </Th> <Td> U.S. Bureau of Reclamation </Td> </Tr> <Tr> <Th_colspan="2"> Dam and spillways </Th> </Tr> <Tr> <Th> Type of dam </Th> <Td> Concrete gravity - arch </Td> </Tr> <Tr> <Th> Impounds </Th> <Td> Colorado River </Td> </Tr> <Tr> <Th> Height </Th> <Td> 726.4 ft (221.4 m) </Td> </Tr> <Tr> <Th> Length </Th> <Td> 1,244 ft (379 m) </Td> </Tr> <Tr> <Th> Elevation at crest </Th> <Td> 1,232 ft (376 m) </Td> </Tr> <Tr> <Th> Width (crest) </Th> <Td> 45 ft (14 m) </Td> </Tr> <Tr> <Th> Width (base) </Th> <Td> 660 ft (200 m) </Td> </Tr> <Tr> <Th> Dam volume </Th> <Td> 3,250,000 cu yd (2,480,000 m) </Td> </Tr> <Tr> <Th> Spillway type </Th> <Td> 2 controlled drum-gate </Td> </Tr> <Tr> <Th> Spillway capacity </Th> <Td> 400,000 cu ft / s (11,000 m / s) </Td> </Tr> <Tr> <Th_colspan="2"> Reservoir </Th> </Tr> <Tr> <Th> Creates </Th> <Td> Lake Mead </Td> </Tr> <Tr> <Th> Total capacity </Th> <Td> 28,537,000 acre ⋅ ft (35.200 km) </Td> </Tr> <Tr> <Th> Active capacity </Th> <Td> 15,853,000 acre ⋅ ft (19.554 km) </Td> </Tr> <Tr> <Th> Inactive capacity </Th> <Td> 10,024,000 acre ⋅ ft (12.364 km) </Td> </Tr> <Tr> <Th> Catchment area </Th> <Td> 167,800 sq mi (435,000 km) </Td> </Tr> <Tr> <Th> Surface area </Th> <Td> 247 sq mi (640 km) </Td> </Tr> <Tr> <Th> Maximum length </Th> <Td> 112 mi (180 km) </Td> </Tr> <Tr> <Th> Maximum water depth </Th> <Td> 590 ft (180 m) </Td> </Tr> <Tr> <Th> Normal elevation </Th> <Td> 1,219 ft (372 m) </Td> </Tr> <Tr> <Th_colspan="2"> Power Station </Th> </Tr> <Tr> <Th> Operator (s) </Th> <Td> U.S. Bureau of Reclamation </Td> </Tr> <Tr> <Th> Commission date </Th> <Td> 1936--1960 </Td> </Tr> <Tr> <Th> Hydraulic head </Th> <Td> 590 ft (180 m) (Max) </Td> </Tr> <Tr> <Th> Turbines </Th> <Td> 13 × 130 MW 2 × 127 MW 1 × 68.5 MW 1 × 61.5 MW Francis - type 2 × 2.4 MW Pelton - type </Td> </Tr> <Tr> <Th> Installed capacity </Th> <Td> 2,080 MW </Td> </Tr> <Tr> <Th> Capacity factor </Th> <Td> 23% </Td> </Tr> <Tr> <Th> Annual generation </Th> <Td> 4.2 TWh (15 PJ) </Td> </Tr> <Tr> <Td_colspan="2"> Website Bureau of Reclamation: Lower Colorado Region - Hoover Dam </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> Hoover Dam </Td> </Tr> <Tr> <Td_colspan="2"> U.S. National Register of Historic Places </Td> </Tr> <Tr> <Td_colspan="2"> U.S. National Historic Landmark </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> Show map of USA West Show map of the US Show all </Td> </Tr> <Tr> <Th> Nearest city </Th> <Td> Boulder City, Nevada </Td> </Tr> <Tr> <Th> Coordinates </Th> <Td> 36 ° 0 ′ 56" N 114 ° 44 ′ 16" W ﻿ / ﻿ 36.01556 ° N 114.73778 ° W ﻿ / 36.01556; - 114.73778 Coordinates: 36 ° 0 ′ 56" N 114 ° 44 ′ 16" W ﻿ / ﻿ 36.01556 ° N 114.73778 ° W ﻿ / 36.01556; - 114.73778 </Td> </Tr> <Tr> <Th> Built </Th> <Td> 1933 </Td> </Tr> <Tr> <Th> Architect </Th> <Td> Six Companies, Inc. (structural), Gordon Kaufmann (exteriors) </Td> </Tr> <Tr> <Th> Architectural style </Th> <Td> Art Deco </Td> </Tr> <Tr> <Th> MPS </Th> <Td> Vehicular Bridges in Arizona MPS (AD) </Td> </Tr> <Tr> <Th> NRHP reference #</Th> <Td> 81000382 </Td> </Tr> <Tr> <Th_colspan="2"> Significant dates </Th> </Tr> <Tr> <Th> Added to NRHP </Th> <Td> April 8, 1981 </Td> </Tr> <Tr> <Th> Designated NHL </Th> <Td> August 20, 1985 </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Hoover Dam </Th> </Tr>

When did they start building the hoover dam
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