 As part of the contract , Six Companies , Inc. was to build Boulder City to house the workers . The original timetable called for Boulder City to be built before the dam project began , but President Hoover ordered work on the dam to begin in March 1931 rather than in October . The company built <unk> , attached to the canyon wall , to house 480 single men at what became known as River Camp . Workers with families were left to provide their own accommodations until Boulder City could be completed , and many lived in <unk> . The site of Hoover Dam <unk> extremely hot weather , and the summer of 1931 was especially <unk> , with the daytime high averaging 119 @.@ 9 ° F ( 48 @.@ 8 ° C ) . Sixteen workers and other <unk> residents died of heat <unk> between June 25 and July 26 , 1931 . 
