Mount Rubidoux, a prominent hill and park beside the Santa Ana River in Riverside, grew from a Southern California excursion destination into one of the city’s defining landmarks. Named for Louis Rubidoux, it was developed as a public park in the early 1900s through efforts led by Frank Miller, with roads, memorials, a summit cross, and scenic overlooks that still shape its character. It gained wider cultural importance through the song A Perfect Day and especially as the site of the United States’ oldest outdoor non-denominational Easter Sunrise service, begun in 1909. Donated to the city in 1955, it remains central to Riverside’s public life.