Which of the following American Presidents was married only once?

Zachary Taylor, 12th President , was married to Peggy Smith on June 21, 1810. He was 25 and she was 21. They had six children. Taylor was a career military man who was a hero of the Mexican War. Although being a slave holder, he was against the spread of slavery into newly acquired territories, earning the ire of Southern politicians. His sudden death in 1850 was viewed as suspicious. An autopsy on his exhumed remains in 1991, however, disproved the theory that he was poisoned.

Theodore Roosevelt, 26th President, was married twice. He married Alice Lee in 1880 when he was 22 and she was 19. Alice died two days after giving birth to their only child in 1884 at the age of 22, the same day that Roosevelt's mother died. Roosevelt married Edith Carrow in 1886, she had been his childhood friend and sweetheart. Roosevelt had a total of 6 children.

James Buchanan, 15th President, is the only Bachelor President. He had been engaged to Anne Caroline Coleman. She broke off the engagement and died shortly afterwards. There are rumors of him being asexual, celibate, or homosexual. But these are speculative. He was a doughface: A Northerner sympathetic to the South. He had no children. His niece, Harriet Lane, served as First Lady.

John Tyler,10th President, was married twice. He was married to Letitia Christian from 1813 to her death in 1844.He married Julia Gardiner in the White House in 1844. He had total of 15 children. Two grandsons are alive today.