Mississippi River. In 1870, blacks made up 36.5% of Austin's population. The postwar period saw dramatic population and economic growth. The opening of the Houston and Texas Central Railway (H&TC) in 1871 turned Austin into the major trading center for the region, with the ability to transport both cotton and cattle. The Missouri, Kansas & Texas (MKT) line followed close behind. Austin was also the terminus of the southernmost leg of the Chisholm Trail, and "drovers" pushed cattle north to the railroad. Cotton was one of the few crops produced locally for export, and a cotton gin engine was located downtown near the trains for "ginning" cotton of its seeds and turning the product into bales for shipment. However, as other new railroads were built through the region in the 1870s, Austin began to lose its primacy in trade to the surrounding communities. In addition, the areas east of Austin took over cattle and cotton production from Austin, especially in towns like Hutto and Taylor that sit over the blackland prairie, with its deep, rich soils for producing cotton and hay. In September 1881, Austin public schools held their first classes. The same year, Tillotson Collegiate and Normal Institute (now part of Huston–Tillotson University) opened its doors. The University of Texas held its first classes in 1883, although classes had been held in the original wooden state capitol for four years before. During the 1880s, Austin gained new prominence as the state capitol building was completed in 1888 and claimed as the seventh largest building in the world. In the late 19th century, Austin expanded its city limits to more than three times its former area, and the first granite dam was built on the Colorado River to power a new street car line and the new "moon towers". The first dam washed away in a flood on April 7, 1900. In the late 1920s and 1930s, Austin implemented the 1928 Austin city plan through a series of civic development and beautification projects that created much of the city's infrastructure and many of its parks. In addition, the state legislature established the Lower Colorado River Authority (LCRA) that, along with the city of Austin, created the system of dams along the Colorado River to form the Highland Lakes. These projects were enabled in large part because the Public Works Administration provided Austin with greater funding for municipal construction projects than