 On December 21 , 1928 President Coolidge signed the bill authorizing the dam . The Boulder Canyon Project Act appropriated $ 165 million for the Hoover Dam along with the downstream Imperial Dam and All @-@ American Canal , a replacement for Beatty 's canal entirely on the U.S. side of the border . It also permitted the compact to go into effect when at least six of the seven states approved it . This occurred on March 6 , 1929 with Utah 's ratification ; Arizona did not approve it until 1944 . 
 On December 21 , 1928 President Coolidge signed the bill authorizing the dam . The Boulder Canyon Project Act appropriated $ 165 million for the Hoover Dam along with the downstream Imperial Dam and All @-@ American Canal , a replacement for Beatty <a href='null_genetive' title='1'><mark>'s</mark></a>canal entirely on the U.S. side of the border . It also permitted the compact to go into effect when at least six of the seven states approved it . This occurred on March 6 , 1929 with Utah <a href='null_genetive' title='2'><mark>'s</mark></a>ratification ; Arizona did not approve it until 1944 . 
On December 21 , 1928 President Coolidge signed the bill authorizing da dam . The Boulder Canyon Project Act appropriated $ 165 million fir the Hoover Dam along witt the downstream Imperial Dam and alll @-@ American Canal , a replacement for Beatty  canal entirely on the U.S. side of the border . It also permitted tdacompact to go into effect when at least six of thdaeven states approved it . This occurred on March 6 , 1929 with Utah  ratification ; Arizona did not approve it till 1944 .