The earliest residents, Native Americans, left artifacts in and around the area that show that Riverside has direct connections to a civilization nearly 6,000 years old. The earliest Europeans visiting the area included the Lewis and Clark expedition. Settlers began filling Riverside's Line Creek valley and surrounding ridges in the 1840s. From its beginning, what is today the city of Riverside included a uniquely diverse population. Several immigrant families from Germany were leaders in pioneering  the area. Later, so many families from Belgium settled in part of Riverside's Missouri River valley that today it is still called the Belgium Bottoms.

Early Riverside played a key role in some of the metropolitan area's most unusual history. Until the 1930s, Riverside was a main stop on one of the nation's longest electric train routes, the 79-mile Interurban ran from North Kansas City to St. Joseph.

Riverside takes its name from several "river side" businesses, including the Riverside Park, a genteel horse race  venue that was built and operated by Kansas City's infamous Tom Pendergast. Ironically, betting and tax problems contributed to the end of "Boss Tom's" career.