The City of Eagle was incorporated on November 2, 1971, and had a population of 3,178. The 2000 US Census for Eagle listed the population at 11,085. The most recent population estimate for Eagle is 20,000.

Eagle is located near the Boise River. The name for the town and nearby island came from the earliest settlers in the valley. Bald Eagles were still prevalent in the valley and an Eagle's nest was spotted in a tall cottonwood tree near the Boise River, thus the name "Eagle Island". The atmosphere is pastoral yet progressive in outlook. Eagle is noted for its mild climate, year around recreational opportunities and friendly people.

Among the first settlers in Eagle was Thomas Hugh Aikens. He was a Nova Scotian of Scottish decent who arrived in Boise by freight team. In Boise, he secured a job with the governmnet engineers who were surveying land tracks. In this position, Mr. Aikens was able to scrutinize property around the valley and in time he found the parcel of land he wanted to buy. In the spring of 1800, Aikens purchased land along Valley Road, which ran from Boise through Middleton. This parcel of land was part of what was to become the City of Eagle. However, at that time, there was only one business building, the Snider Blacksmith Shop.

It was at this point that the situation arose that was a decisive factor in the establishment of the community. The people in the vicinity of Eagle Island appealed to the county for a bridge. The request was granted, but then a question arose: "Where shall the bridge be located?" Shall the Eagle Island bridge be near Eagle or Star? The County Commissioners passed the buck to the populace, and it was decided to put it to a vote. Star was forging ahead in the balloting until the strategy and political acumen of Mr. Aiken was demonstrated . Hiring , at his own expense, a luxurious horsedrawn carrier, he went to the Old Soldier's Home and transported veterans to the polls. Their vote was the deciding factor and placed the Eagle Island Bridge where it now stands.