We recorded and analyzed the songs of 23 male House Finches (Carpodacus mexicanus) at six sites in Sioux County in far northwestern Iowa. We compiled a catalogue of all the syllables detected in the population and examined the extent of syllable sharing and song sharing among individuals both within sites and between sites. Unlike in a population of House Finches studied in Colorado, we found no significant difference between the level of syllable sharing within sites and between sites and no relationship between the extent of syllable sharing and distance between birds. Over 67% of the House Finch syllables recorded previously in eastern Iowa were found in Sioux County, and all House Finches in Sioux County shared two major song themes that were similar to themes found in eastern Iowa. Our findings suggest that the House Finches in Sioux County originated from eastern populations of the species, corroborating the colonization patterns that have been inferred from Breeding Bird Surveys and Christmas Bird Counts.