Horn died Thursday at his Long Beach home from complications of Alzheimer's disease, said his son, Steve Horn Jr.
On Capitol Hill, Horn was regarded as a maverick known for his bipartisanship during five terms in Congress from 1993 to 2003.
Although he voted to impeach President Clinton, Horn often broke ranks with his party, including voting against oil drilling in the Arctic National Wildlife Refuge. He also supported abortion rights and gun control.
"I have fought for all the people, not just Republicans," Horn told The Times in 2000.
Locally, he spearheaded funding for a major flood-control project and for construction of the Alameda Corridor, an express route to move cargo from ports to rail yards near downtown Los Angeles.
After the boundaries of his Democratic-trending 38th Congressional District were redrawn in 2001, he decided against seeking another term. At the time, the district included Bellflower, Downey, Paramount, Signal Hill and most of Lakewood and Long Beach.
At Cal State Long Beach, Horn served as president from 1970 to 1988, an era of tremendous growth for the school.
During Horn's tenure, "the university grew in stature and distinction," F. King Alexander, president of Cal State Long Beach, said in a message to the campus.
In addition to overseeing a huge building boom on campus, Horn emphasized faculty development, launched pioneering services for disabled students and established a program that allows students age 60 or older to attend classes at reduced cost.
In 2003, Cal State Long Beach honored Horn and his wife by naming a building the Steve and Nini Horn Center; it houses an art museum.
He was born John Stephen Horn on May 31, 1931, in San Juan Bautista, Calif.
After earning a bachelor's degree in political science in 1953 at Stanford University, he earned a master's in public administration at Harvard University in 1955 and a doctorate in political science at Stanford in 1958.
Because he was a scholar of Congress, Horn was motivated to work in the Eisenhower administration in the 1950s and for then-Sen. Thomas Kuchel from 1960 to 1966, his son said.
As the chief legislative aide for Kuchel, a moderate Republican from California, Horn was "very involved" in working on such landmark legislation as the Civil Rights Act of 1964 and the Voting Rights Act of 1965, his son said.
Horn's collection of books on Congress and U.S. history numbered nearly 10,000 volumes, including three that he wrote on congressional ethics, budgeting and organization.
In addition to his son, Steve, of Long Beach, Horn is survived by his wife of 57 years, Nini Moore Horn; a daughter, Marcia Horn of Phoenix; and a grandson.
Services will be private. A public memorial is being planned.