Colorado River too much of the lower basin allotment; in 1944 a compromise was reached in which Arizona would get a firm allocation of , but only if California's allocation was prioritized during drought years. These and nine other decisions, compacts, federal acts and agreements made between 1922 and 1973 form what is now known as the Law of the River. On September 30, 1935, the United States Bureau of Reclamation (USBR) completed Hoover Dam in the Black Canyon of the Colorado River. Behind the dam rose Lake Mead, the largest artificial lake in the U.S., capable of holding more than two
Steamboats of the Colorado River Mexico Territory, and Nevada state. They remained the primary means of transportation of freight until the advent of the more economical railroads began cutting away at their business from 1878 when the first line entered Arizona Territory. Steamboats were tried on the upper Colorado River: in Glen Canyon; on the Green River in Utah and Wyoming; and on the Grand River, (renamed as the upper part of the Colorado River after 1921), above its confluence with the Green River in Utah and in Colorado. These attempts in the late 19th Century and early 20th Century met with little success. The