Harry Martens Jr., 86, who guided the nearly century-old L.P. Steuart automotive business before retiring last year, died from complications of Alzheimer's disease July 3 at the ManorCare nursing home in Potomac. He lived in Chevy Chase until a year ago.

Mr. Martens was president of L.P. Steuart Inc., a successful Washington business founded by two brothers in 1904 from a mule-drawn cart that sold coal in the winter and ice in the summer. Between 1908 and 1912, the family began to sell Henry Ford's Model T, according to a Washington Post article in April. The family opened a Ford dealership at 1440 P St. NW along what was known as "Auto Row" before World War II and later became the oldest and largest Chrysler-Plymouth dealer in the Washington area.

The Steuart brothers, Leonard P. and Guy T., eventually owned 20 companies valued in the millions of dollars. Their business ventures included automobile dealerships, insurance and investment companies and petroleum.

Mr. Martens joined the business in 1946, after marrying one of L.P. Steuart's two daughters, Virginia. He started at the bottom, rolling tires at the Steuart Chrysler dealership on P Street. He then moved to the parts department and the used-car lot before graduating to the new-car showroom and the sales side of the business.

Over the decades, the family business sold a variety cars, including Oaklands, DeSotos, Packards, Chevrolets, Plymouths, Pontiacs, Jensen Healeys, Datsuns and Subarus. In 1956, Mr. Martens switched the Chrysler dealership to Volvo.

While other dealerships left the city for the suburbs, Martens Volvo stayed put at its Tenleytown address in Northwest Washington, selling Volvos and Volkswagens. In a 1997 interview with Washington Business Journal, Mr. Martens said: "We've never really been tempted to leave. It's still a good location for us."

At the pinnacle of his career, Mr. Martens was president of the Steuart family corporation, a conglomerate of automobile agencies, taxicab associations, auto parts distributors and an insurance company.

His children now carry on the family business, managing automotive dealerships and service centers in Washington and Bethesda.

Mr. Martens was born in Milwaukee and attended the University of Wisconsin, where he was a member of Chi Psi fraternity. He served as an Army captain in World War II at Edgewood Arsenal in Maryland.

He served on the boards of the D.C. Board of Trade, the Boy Scouts and the National Automobile Dealers Association. He was a director of the Montgomery County chapter of the American Red Cross and the Metropolitan Police Boys and Girls Clubs.

He was a member of the Friendly Sons of St. Patrick, Rotary Club, Columbia Country Club, Burning Tree Club and the University Club of Washington. He also served as potentate of Almas Shrine Temple in Washington, postmaster of the Temple Noyes Masonic Lodge and past director of the Royal Order of Jesters.

Survivors include his wife of 58 years, of Chevy Chase; five children, Chris Martens of Potomac, Dana Martens of Bethesda and Steuart Martens, Harry Martens III and Ginger Martens, all of Rockville; and 10 grandchildren.