In 1883, the landscape of what was to become Canyon County, Idaho was changed forever when the Oregon Short Line Railway built a line from Granger, Wyoming to Huntington, Oregon. The sagebrush-covered ground was cleared and leveled so that tracks could be laid, and towns began to spring up every 10 to 15 miles along the tracks, including Nampa.

Many early residents called it New Jerusalem because of the large religious community.

The Shoshone originated in the western Great Basin and spread north and east into present-day Idaho and Wyoming. Led by Chief Pocatello, they fought during the 1860s against settlers in Idaho. As more settlers encroached on Shoshone hunting territory, the natives raided farms and ranches for food and attacked immigrants. In 1863, these skirmishes led to the Bear River Massacre, in which the U.S. Army attacked and killed an estimated 250 Shoshone, who were at their winter encampment. A large number of the dead were non-combatants, including children.

The name "Nampa" is believed to have come from the Shoshone word "namb", which means either either moccasin or footprint. Native Americans in the region were known to stuff their moccasins with or wrap their feet in sage brush to insulate against the frozen winter ground, making their footprints larger.

Nampa's founders, Alexander and Hannah Duffes, were very religious and refused to sell building lots to anyone who wanted to build a saloon. Nevertheless in 1888, of the 28 buildings that made up the town, 3 were saloons. Ironically, after the Duffes passed away in 1909, their home was removed and a brewery was built in its place.

The Snake River Stampede had its humble beginnings as a bucking contest in conjunction with Nampa's harvest festival. Today, it is one of the top 12 rodeos recognized by the Professional Rodeo Cowboys Association.

The building that houses Pete's Tavern in historic downtown Nampa has been around for over a century. During the Prohibition era, it served as a speakeasy. While only shadows have been seen, many visitors to the tavern have reported hearing whispers and feeling light touches by an invisible hand. According to a report from local television station KTVB, paranormal investigators have recorded four distinct disembodied voices in the tavern's back room, which is known as "The Cave".

Nampa's Great Fire of 1909 occurred along Front Street in the Business District directly across from the Nampa Train Depot between 12th and 13th Streets. It was July 3rd, and the city was gearing up for an exciting 4th of July fireworks display the following day, but the show started early when a customer in the Arnold Cigar store decided to light a firework inside the store. Mr. Arnold snatched the firework and attempted to throw it onto Front Street, but it was too late. The firework exploded in the store and caught fire to other fireworks. During the next three hours, the entire block went up in flames, and half of Nampa's businesses were wiped out.

Many area residents have fond memories of sipping an Orange Julius, sitting on Santa's lap, or playing games at the Red Baron arcade in Karcher Mall, which was "the place to gather" for several decades. It was the largest shopping mall in the Treasure Valley until the Boise Towne Square mall was built in Boise in 1988, drawing business away.

Known locally as "The Heart of the Treasure Valley", Nampa is about a 20 mile drive to Boise, and only 10 miles from smaller towns such as Meridian, Caldwell, Kuna, and Marsing.