Finally, 36 years after his Mercury flight, in the last months of his final Senate term, he got his wish for a return to orbit. Despite some criticism that his presence on the mission was a political payoff, a waste of money and of doubtful scientific merit, the hero of yesteryear brought out the crowds again, cheering out of nostalgia and enduring respect as he was launched aboard the space shuttle Discovery on Oct. 29, 1998. At 77, he became the oldest person to go into space.

In retirement from the Senate, Mr. Glenn lived with his wife of 73 years, Anna (he always called her Annie), in a suburb of Washington in addition to Columbus. Ohio State University is the repository of papers from his space and political careers.

“John always had the right stuff,” President Obama said in a statement on Thursday, “inspiring generations of scientists, engineers and astronauts who will take us to Mars and beyond — not just to visit, but to stay.”

The Making of a Hero

John Herschel Glenn Jr. was born on July 18, 1921, in Cambridge, Ohio, the only son of a railroad conductor who also owned a plumbing business, and the former Clara Sproat. A few years later, the Glenns moved to New Concord, a small town in southeastern Ohio with a population of little more than 1,000.

“It was small but had a lot of patriotic feeling and parades on all the national holidays,” Mr. Glenn once said. “Wanting to do something for the country was just natural, growing up in a place like New Concord.”

Like most everyone else there, the Glenns lived through the hard times of the Depression, instilling in their son a rigid moral code based on their own God-fearing example and saw him through an apple-pie boyhood. He played trumpet, sang in the church choir, washed cars for pocket money and worked as a lifeguard. In high school (now named for him), he was an honor student and lettered in football, basketball and tennis.

He still had time to court his high school sweetheart, Anna Margaret Castor, the doctor’s daughter. It did not matter that she stammered; she was his girl, and he loved her. They married in April 1943, and he often called her “the real rock of the family.” From the time they came to public attention, and throughout the turbulence of spaceflight and politics, John and Anna Glenn each seemed the other’s center of gravity.