other Texas cities. During the early twentieth century, a three-way system of social segregation emerged in Austin, with Anglos, African Americans and Mexicans being separated by custom or law in most aspects of life, including housing, health care, and education. Many of the municipal improvement programs initiated during this period—such as the construction of new roads, schools, and hospitals—were deliberately designed to institutionalize this system of segregation. Deed restrictions also played an important role in residential segregation. After 1935 most housing deeds prohibited African Americans (and sometimes other nonwhite groups) from using land. Combined with the system of segregated public services, racial segregation increased in Austin during the first half of the twentieth century, with African Americans and Mexicans experiencing high levels of discrimination and social marginalization. In 1940, the destroyed granite dam on the Colorado River was finally replaced by a hollow concrete dam that formed Lake McDonald (now called Lake Austin) and which has withstood all floods since. In addition, the much larger Mansfield Dam was built by the LCRA upstream of Austin to form Lake Travis, a flood-control reservoir. In the early 20th century, the Texas Oil Boom took hold, creating tremendous economic opportunities in Southeast Texas and North Texas. The growth generated by this boom largely passed by Austin at first, with the city slipping from fourth largest to tenth largest in Texas between 1880 and 1920. After a severe lull in economic growth from the Great Depression, Austin resumed its steady development. Following the mid-20th century, Austin became established as one of Texas' major metropolitan centers. In 1970, the U.S. Census Bureau reported Austin's population as 14.5% Hispanic, 11.9% black, and 73.4% non-Hispanic white. In the late 20th century, Austin emerged as an important high tech center for semiconductors and software. The University of Texas at Austin emerged as a major university. The 1970s saw Austin's emergence in the national music scene, with local artists such as Willie Nelson, Asleep at the Wheel, and Stevie Ray Vaughan and iconic music venues such as the Armadillo World Headquarters. Over time, the long-running television program Austin City Limits, its namesake Austin City Limits Festival, and the South by Southwest music festival solidified the city's place in the music industry. Geography Austin, the southernmost state capital of the contiguous 48 states, is located in Central Texas on the Colorado River. Austin is northwest of Houston, south of Dallas