Daniel Aaron, a literary critic and historian who helped preserve the nation’s cultural heritage as a co-founder of the nonprofit Library of America and who pioneered the multifaceted academic field of American studies, died on Saturday in Cambridge, Mass. He was 103.

The cause was complications of pneumonia, his daughter-in-law Anna Aaron said.

Professor Aaron suggested in his autobiography that his chosen profession was augured when he was only 3, with the sinking of the British ocean liner Lusitania by a German U-boat in 1915.

The victims included his mother’s mentor, Elbert Hubbard, a journalist who had founded the Roycroft artisan community in upstate New York in the late 19th century with his wife, Alice. Elbert Hubbard also wrote the best-selling inspirational essay “A Message to Garcia,” about the prelude to the Spanish-American War.

Hearing about the sinking while growing up “foreshadowed my introduction to American history,” Professor Aaron wrote in the memoir, “The Americanist” (2007). But his route to being granted one of the first doctoral degrees in American civilization by Harvard and becoming an English professor at Smith College and Harvard was, much like history itself, hardly preordained.