By 1930 the village of Ammon had 270 inhabitants, but the total district of Ammon, which is how the name is usually used and is closer to the modern borders, had a population of about 1100. Ammon was founded by members of The Church of Jesus Christ of Latter-day Saints in 1888. It was originally called South Iona because it was the dependent branch in the south end of the Iona, Idaho ward. The area was made a ward in the church in 1889 with Arthur M. Rawson as bishop, who renamed the town in honor of Ammon, a figure in the LDS book of scripture, the Book of Mormon. Since it was now independent of the Iona Ward, a new name seemed appropriate. On February 9, 1893, the name of the town was changed from South Iona Ward to Ammon.