Hudson's Bay Company established Fort Boise in 1834 near what is now Parma,[4] but abandoned it in 1855.

[5] Discovery of gold in the Boise Basin in 1862 brought settlement to the region again.

[7][8] The arrival of the railroad at Caldwell led to the establishment of a town there as of August 1883.

[9] Businessmen James A. McGee and Alexander Duffes filed the plat for nearby Nampa in 1886.

[10] Parma was settled around the same time, with the Old Fort Boise post office being moved to the town's location; it was incorporated in 1904.

[11] Ada County established precincts for each of the settlements with a combined 1890 Census population of 2,311.

[18] Some sources attribute the name to the canyon of the Boise River near Caldwell, while western writers John Rees and Vardis Fisher believed it was named for the Snake River canyon, which forms a natural boundary with Owyhee County to the south and west.

19.80% of all households were made up of individuals, and 8.40% had someone living alone who was 65 years of age or older.

Like the majority of Idaho, Canyon County is reliably Republican by comfortable margins.

The last time a Democratic candidate carried the county was in 1936 by Franklin D. Roosevelt.

In elections, Republican candidates usually achieve approximately two-thirds of the vote from Canyon County.

School districts include:[30] Residents are in the area (and the taxation zone) for College of Western Idaho.