Gustav (Gus) Wilke, builder of the state Capitol, was born in the village of Ludershaden near Stralsund, Pomerania, on the Baltic Sea on October 1, 1853, the son of John (Johann) and Sophia (or Sophie) Wilke. The family, afraid of the potential for war in the Germanic states, moved to the United States in 1868, arriving in New York in July of that year; they settled in Chicago by 1869. Wilke married Mary Bernahl on October 18, 1877, and they became the parents of three children. Wilke had attended a building-trades school in Germany before coming to the United States; in Chicago he worked in the office of architect Theodore Vigo Wadskier. In the early 1870s Wilke joined his father's contracting business, and they did considerable work in Chicago after most of the city burned in 1871. One of their other joint projects was the construction of the museum building at the University of Michigan at Ann Arbor in 1880. In 1882 Wilke received a subcontract from Abner Taylor, the assignee of Taylor, Babcock and Company of Chicago, to build the foundation and basement walls of the Texas state Capitol. His work was so good that he received several other subcontracts to complete the Capitol project. Wilke also oversaw the construction of the Austin to Oatmanville (Oak Hill) rail line, as well as a branch line from Burnet to Granite Mountain near Marble Falls, both of which were built to facilitate the transport of large quantities of limestone and granite needed in the construction of the Capitol. Two of his more controversial decisions while working on the Capitol concerned his use of convict labor and his importing stonecutters from Scotland (see CAPITOL BOYCOTT). In 1893 Wilke paid a fine for his violation of the Contract Labor Law of 1885.
The Capitol was completed in May 1888, but the committee overseeing the project refused to accept it until several problems, including a leaky roof, were fixed. Wilke stayed in Texas to make these corrections, which he completed in December 1888 along with other work. In the fall of 1888 he completed a new depot on the west side of Congress Avenue between Second and Third streets in Austin for the International-Great Northern Railroad. In early 1889 he received a contract from the Brazos River Channel and Dock Company for the construction of jetties at the old mouth of the Brazos River. During that year he and his family lived at Quintana, near Brazoria. Wilke's Texas projects made him a millionaire. When he returned to Chicago in 1890, he built his wife a two-story, red granite mansion in the Lake View area of Chicago. He conducted a successful contracting business in Chicago, although much of his work took him to other cities. Wilke became one of the first builders to make use of the skyscraper technology developed by William Le Baron Jenney. He built the Cullom Memorial Building at West Point (1895–98), the Traction Terminal Building in Indianapolis (1903–04), the Memphis Trust Company Building in Memphis (1904–05), the Denver Public Library (1907), the Scanlan Building in Houston (1910), the Putnam Building in Davenport, Iowa (1910), and the Union Trust Building in Cincinnati (1915). Wilke was a Lutheran, a thirty-second degree Mason, and a member of the Schwaben Verein and other fraternal orders. He also belonged to the Harmonic, Orpheum, and Fedelia singing organizations in Chicago. Wilke died in Chicago on April 24, 1915, and was interred at Graceland Cemetery in a red granite mausoleum that he had provided for his family in 1896.