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

Eldora is the county seat of Hardin County, which was established on January 15, 1851. The county was named in honor of Colonel John J. Hardin of Illinois, who was killed in the Mexican War. The name Eldora purportedly came from one of the daughters of the Edgington family who first settled in the area. Between 1856-1891, several challenges for the site of the county seat occurred, but ultimately, Eldora prevailed. In Hardin County, Eldora, Alden, and Iowa Falls all received Carnegie grants.

(Source: Pratt, LeRoy G. “The Counties and Courthouses of Iowa.” Mason City, Ia; Klipto Printing & Office Supply Company, 1977, p. 147-148.)