During World War II, the U.S. needed vast amounts of electricity for heavy industry, and TVA met that need by building 12 hydroelectric plants and one steam plant at the same time, helping the nation build 50,000 planes for U.S. air forces and generating millions of kilowatts of energy for uranium enrichment at Oak Ridge, Tennessee, a secret Manhattan Project site that helped produce the first atomic bomb. In the 1930's, TVA also focused on completing the dams that would make the Tennessee River navigable between Paducah, Kentucky, and Knoxville, Tennessee; as construction of Guntersville Dam began in 1935 while Wheeler Dam was being finished and Pickwick Dam was under construction, Guntersville faced disruption to its lumber and cotton commerce when the lake was filled, so a large dike was built to protect the town and allow industry to prosper by moving goods on the river instead of across it. The project brought painful sacrifices as the federal government purchased 110,145 acres and nearly 1,200 families, along with numerous graves and cemeteries, were relocated to higher ground in the county, but it also brought work for over 2,000 men building the dam and a small lock later expanded in 1965. By the end of World War II, TVA had profoundly changed the Tennessee Valley through navigation improvements and widespread electric power, making daily life easier, attracting new industries and jobs, and establishing itself as the nation's largest electric power supplier before later becoming a self-financed agency that receives no federal tax dollars.