Wikipedia served as the source for the population information. Note that the population increased between 1900 and 1910.

Iowa City is the county seat of Johnson County, which was established on December 21, 1837. The county was probably named for Colonel Richard M. Johnson (1780-1850) who had served as Vice President of the United States under President Van Buren. In 1838, the town of Napoleon was chosen as the seat of justice. In 1839, a site two miles north of Napoleon was chosen as the capital of the Territory of Iowa. The site was named Iowa City and it became the county seat of Johnson County as well as the capitol of new state until 1857 when the capitol was moved to Des Moines.

(Source: Pratt, LeRoy G. “The Counties and Courthouses of Iowa.” Mason City, Ia; Klipto Printing & Office Supply Company, 1977, p. 178.)