The letters are Mr. Peavoy’s only link to his former pen pal. They never visited or exchanged a single phone call during their four years of college. They lost touch entirely after graduation, except for the 30-year reunion of the Maine South High School class of 1965, held in Washington to accommodate the class’s most famous graduate, whose husband was then serving his first term in the White House.

“I was on the White House Christmas card list for a while,” Mr. Peavoy said. Besides a quick receiving-line greeting from Mrs. Clinton at the reunion, Mr. Peavoy has had just one direct contact with her in 38 years. It was, fittingly, by letter, only this time her words were more businesslike.

In the late 1990s, Mr. Peavoy was contacted by the author Gail Sheehy, who was researching a book on the first lady. He agreed to let Ms. Sheehy see the letters, from which she would quote snippets in her 1999 biography, “Hillary’s Choice.” When Mrs. Clinton heard that Mr. Peavoy had kept her old letters, she wrote him asking for copies, which he obliged. He has not heard from her since.

“For all I know she’s mad at me for keeping the letters,” said Mr. Peavoy, a pack rat who says he has kept volumes of letters from friends over the years. A Democrat, he said he was undecided between supporting Mrs. Clinton and Senator Barack Obama.

Ms. Rodham’s letters are written in a tight, flowing script with near-impeccable spelling and punctuation. Ever the pleaser, she frequently begins them with an apology that it had taken her so long to respond. She praises Mr. Peavoy’s missives while disparaging her own (“my usual drivel”) and signs off with a simple “Hillary,” except for the occasional “H” or “Me.”

As one would expect of letters written during college, Ms. Rodham’s letters display an evolution in sophistication, viewpoint and intellectual focus. One existential theme that recurs throughout is that Ms. Rodham views herself as an “actor,” meaning a student activist committed to a life of civic action, which she contrasts with Mr. Peavoy, who, in her view, is more of an outside critic, or “reactor.”

Image John Peavoy, now an English professor at Scripps College, holding some of the letters from Hillary Rodham. Credit... Axel Koester for The New York Times

“Are you satisfied with the part you have cast yourself in?” she asks Mr. Peavoy in April 1966. “It seems that you have decided to become a reactor rather than actor — everything around will determine your life.”