The park is three miles (4.8 km) north of Merriman in Cherry County, near the South Dakota border.
Arthur and Eva met when her car broke down near his ranch and he came to her assistance.
They married in 1928 and kept the ranch running while each served in a variety of public offices.
Concerned that it would be fragmented to new owners, the former Senator willed her ranch to the state in memory of her husband.
The ranch house and outbuildings have been preserved, and a large visitor center documenting the Bowrings' lives is on the site.