There are suitable places for stargazing near Riverside, California. Below are recommended locations and information about each:

Twentynine Palms, CA
This national park, located about 80 miles (130 km) east of Riverside, has minimal light pollution, making it ideal for stargazing. It is especially famous for its clear views of the Milky Way at night. 

Palomar Mountain, CA
Located about 75 miles (120 km) south of Riverside, this observatory is open to the public and allows stargazing on clear days. It is advisable to check the operating hours before visiting. 

Arcadia, CA
This national forest, located about 60 miles (97 km) northwest of Riverside, offers dark skies away from the city's light pollution. You can enjoy stargazing along with camping. 

Death Valley, CA
This national park, located about 200 miles (320 km) northeast of Riverside, boasts one of the darkest skies in the United States and is known as an excellent location for stargazing. 

When planning your stargazing, it is recommended to check the weather and moon phases, and to visit with the necessary equipment for safety.