Calvin Larson’s day job was practicing bankruptcy law in Fairfax County. He was a zealous physical fitness enthusiast who on temperate days swam to work. Until he was 85, he also had a paper route, delivering daily copies of The Washington Post early in the morning with the help of his dog Guinness, a 90-pound mongrel, half pit-bull, half labrador.

He was a civic activist, and he was one of the early residents of what 50 years ago was the “new town” of Reston, Va., where he was a founder of the Reston Community Association and the Reston Music Center, a program that organizes summer studies for teenage musicians with professional musicians. He volunteered at homeless shelters and at the Whitman-Walker clinics for AIDS patients, where he also did pro bono legal work. In 1985, the county Board of Supervisors honored him for his civic work, one of several community honors.

Mr. Larson died Dec. 3 at his home in Reston at 96. The cause was congestive heart failure, said a grandson, Galen Mook.

Calvin Frederick Larson was born Sept. 28, 1923, on a dairy farm operated by his parents near Weyauwega, Wis., grew up in a house without indoor plumbing and went to a one-room school house.

He attended the University of Wisconsin but left during World War II for service in a special Army engineering unit based at Brown University in Rhode Island. The unit never left North America but instead was sent to California during the summers to pick grapes and to Quebec in the winters to learn French and ski, Mr. Larson’s family said. After his discharge, he graduated from Wisconsin in 1948.

He was public relations director of the Rocky Mountain chapter of AAA before graduating from the University of Denver law school in 1965.

He married Nancy Nugent in 1951. In addition to his wife, of Reston, survivors include two children, Sarah Larson of Reston and Barbara Zaczek of Manhattan, Ill.; five grandchildren; and four great-grandchildren.

In 1967, Mr. Larson settled in Reston, drawn by the vision of its founder, Robert E. Simon Jr., of a planned racially and economically integrated community where residents could work where they also lived and played.

Until he was in his 90s, he practiced law in an office overlooking Lake Anne Village Center. Most mornings, his family said, he swam to work from his home about a half-mile away on Lake Anne, changing from his Speedo swimwear to a three-piece suit once he got to the office.

In 2009, Mr. Larson gave up the 100-customer paper route he had held for 18 years. He took it on thinking he would eventually pass it on to his grandchildren.

They did not want it.

“I wasn’t going to get up at 3 in the morning,” said Galen Mook.