Ruth, who lived in Rolling Hills, died Friday at Torrance Memorial Medical Center from a massive brain hemorrhage, his family said.
In 1975, he and Bill Tooley became partners in Tooley & Co. He served as the firm's president from 1984 until 1998, when it was acquired by Texas real estate giant Trammell Crow Co. for $23.3 million.
Tooley & Co. specialized in business centers and office structures that were often used as a company's headquarters. Other major projects included the Jamboree Center in Irvine and the Howard Hughes Center on the Westside.
He once said his philosophy regarding business -- one that valued accentuating the positive and achieving excellence above growth and profits -- was inspired by his daughter Ann, who became a quadriplegic at a young age in a gymnastics accident yet maintained an upbeat approach to life.
"Like Annie, I try to attack life, to make something good happen every day, to relish and appreciate every moment -- and I try to instill what Annie's inspiration means for me in our people," Ruth told the Los Angeles Business Journal in 1993.
He was born Clarence Miller Ruth Jr. on July 18, 1930, in Scranton, Pa., one of three children of Clarence Ruth, who owned a bakery, and his wife Kathryn, a schoolteacher.
At Ohio's Muskingum College, he was a standout athlete in football, basketball and baseball, the school confirmed.
After earning his bachelor's in psychology in the early 1950s, Ruth joined the Marine Corps and served in the Korean War until 1953.
In the late 1950s, he worked as an assistant athletic director at Northwestern University and met Marion Nelson, whom he married in 1958.
While in Los Angeles for a Rams game, Ruth ended up watching it on TV at a friend's real estate office. By game's end, he had sold three houses and soon decided to move west.
At one point, he led a 160-person team at Tooley. Many of Ruth's hires weren't obvious choices, said his son Bill.
"He was a phenomenal judge of character," his son said. "He would meet a waitress or parking attendant and know that they had something bigger inside of them. Once he hired somebody, they stayed. He was always about the people."
In addition to his son Bill, and daughter Ann, Ruth is survived by his wife, Marion; two other children, Bob and Lee; and five grandchildren.
A memorial service will be held at 11 a.m. July 8 at Rolling Hills Covenant Church, 2222 Palos Verdes Drive North, Rolling Hills Estates.
Instead of flowers, the family suggests donating to a fund established in Ruth's name with the Marine Corps Scholarship Foundation, www.mcsf.com.