When Illinois entered the Union in 1818, the future site of Springfield was still unbroken prairie. The first settler was Elisha Kelly, who came from North Carolina in 1819. The settlement became the seat of Sangamon County in 1821. With the support of Abraham Lincoln, who called Springfield his home at that time, the city became the capital of Illinois in 1837. Railroads arrived in 1852, which led to an increase in economic activity. When Lincoln left to take the office of president in 1861, the population had risen to nearly 10,000. Soon after the Civil War, the first coal mine shaft was sunk in Springfield, which opened an industry that became important to the area. The state capitol building was constructed from 1868 to 1887. Most state offices were housed in the capitol until the Centennial Building was erected in 1923. A large civic project was the construction of a lake, completed in 1930, to provide water and electric power. Springfield is the home of the Abraham Lincoln Presidential Library and Museum, Illinois State Museum, Oliver P. Parks Telephone Museum, and the Lincoln Tomb. Springfield also is the home of the National Cash Register Company, where the first mechanical cash registers were invented, dating to 1884. Mary Todd Lincoln, widow of Abraham Lincoln, died in Springfield in 1882.