William Steuart was born in 1861 in Texas, on a ranch that his parents were homesteading. When his father died, a young Steuart and his mother traveled back east, settling in the District of Columbia. He graduated from George Washington University (then known as Columbian) in 1884, eventually being admitted to the District of Columbia and Maryland bars.

Steuart was deeply involved in census activities for much of his adult life. During the 1880 census, he worked as an assistant to superintendent Francis A. Walker, attending night school at the same time. He left his law practice in 1890 in order to become chief of the manufacturing division. In 1900, he was chief statistician for that division.

From when the Census Office became a permanent bureau in 1902 until 1917, Steuart served as chief statistician for census of manufactures. He was secretary and statistician at the U.S. Tariff Commission from 1917 to 1919, before returning to the Census Bureau to become assistant director, a position created by the 1920 Census Act.

When President Harding appointed Herbert Hoover his new secretary of commerce in 1921, Hoover replaced most of the agency heads under his control, including director of the census Samuel Rogers. Hoover replaced Rogers with Steuart, who was the assistant director at the time. Steuart served as director of the Census Bureau until 1933 - two years past the mandatory retirement age. He died in 1956.