The original building was cruciform, with a central rectangle 76 feet (23 m) wide by 85 feet (26 m) deep (23 x 25.8 m). It had two wings, each 35 feet (11 m) wide by 52 feet (16 m) deep (10.6 x 15.8 m). The windows' glass panes are made of 26-ounce (737 g) French crystal, as are those above the doors. Floors and wainscotting are of Alaskan marble, shipped to San Francisco in 20-ton (18,144 kg) blocks and there cut and polished for installation.

The first floor contained a major office at each corner connected by central halls, while the wings of the second floor were filled by the two legislative chambers—the Assembly and the Senate. The octagonal dome topped with a cupola admitted light to the second story. During 1906, an octagonal Annex was added to the rear (east) of the capitol to house the State Library.

By the early 20th century, the legislature had outgrown the capitol, and prominent Nevada architect Frederic DeLongchamps was contracted to design northern and southern legislative wing-annexes, completed in time for the 1915 session. These compatible wings used stone from the same quarry as the original portion of the capitol, and provided more office space and expanded legislative chambers.

For more than 50 years, all three parts of the state government were housed in the Capitol. The Supreme Court met here until 1937, when it relocated into an adjacent building, and the Nevada Legislature met here until 1971, when it relocated to its new Legislative Building just south of the Capitol. Every Nevada governor except the first has had his office in the capitol. Nowadays, the Capitol continues to serve the Governor, and contains historical exhibits on the second floor.