The city is named for its location beside the Santa Ana River. Like the Los Angeles and San Gabriel rivers to the north, the Santa Ana is lined with concrete in many places. A notable feature on the river is the Seven Oaks Dam, which, at 632 feet (193 m) tall, is the 6th tallest dam in the United States.

In the late 1700s and early 1800s the area was inhabited by Cahuilla and the Serrano people. The first encounter with Europeans was in 1774, when Juan Bautista de Anza was looking for a trade route between Sonora and Monterey in Alta California.

The first orange trees were planted in 1871, with the citrus industry Riverside is famous for beginning three years later when Eliza Tibbets received three Brazilian navel orange trees from a personal friend, William Saunders, who was a horticulturist at the United States Department of Agriculture in Washington, D.C. The trees came from Bahia, Brazil. The Bahia orange did not thrive in Florida, but its success in southern California was phenomenal. By 1882, there were more than half a million citrus trees in California, almost half of which were in Riverside.

As the city grew, a small guest hotel modeled after the missions left along the California coast by Franciscan friars in the 18th and 19th centuries, known as the Glenwood Tavern, eventually grew to become the Mission Inn. Pat and Richard Nixon were married in what is now the Presidential Lounge, Nancy and Ronald Reagan honeymooned there, and eight other U.S. presidents have visited the inn: Benjamin Harrison, William McKinley, Theodore Roosevelt, William Howard Taft, Herbert Hoover, John Fitzgerald Kennedy, Gerald Ford, and George W. Bush.

Riverside is the home of the "World's Largest Paper Cup" (actually made of concrete), which is over three stories (68.10 ft; 20.76 m) tall. The "Dixie Cup" landmark is located on Iowa Street just north of Palmyrita, in front of what was once the Dixie Corporation's manufacturing plant.

Known as the city of arts and innovation, Riverside visitors and residents enjoy cultural activities including downtown museums, restaurants and performing arts centers.

Although Frederick Law Olmsted, who designed New York City's Central Park, had died in 1903, his design principles were evident in his sons' planning of Fairmount Park. The primary design aspects of the park were implemented over the following 13 years, ending in 1924 with Lake Evans.

Several religious celebrations take place on top of Mount Rubidoux. One is an annual Easter Sunrise service, which is the nation's oldest continual non-denominational outdoor Easter service. The 100th anniversary of the event was held April 12, 2009. In addition, a 2½-mile (4 km) procession is held each December from Our Lady of Guadalupe Shrine to the top of Mount Rubidoux to promote awareness of Juan Diego's walk up Tepeyac hill, in 1531, where he reportedly saw a Marian apparition known as Our Lady of Guadalupe.

Unfortunately, Riverside sits in a "smog belt," caused primarily by wind patterns that blow wind from the Los Angeles Basin into the Inland Empire.

Riverside's close proximity to Hollywood, combined with its many unique architectural features, has made it a frequent filming location, starting with the 1919 silent comedy Boots, which starred Dorothy Gish as a young shoeshine girl who foils a plot to blow up a government official. It was filmed at the Mission Inn.