Nampa is the most populous city in Canyon County, Idaho, United States. Its population was 100,200 at the time of the 2020 census. It is Idaho's 3rd most populous city. Nampa is about 20 miles west of Boise along Interstate 84, and six miles west of Meridian. It is the second principal city of the Boise metropolitan area. The name "Nampa" may have come from a Shoshoni word meaning either moccasin or footprint. According to toponymist William O.