The following is a list of the oldest men tennis players to ever win titles at the U.S. Open. As you can see below, the oldest man to win the U.S. Open in the Open Era was not terribly old when he won.
I've been playing tennis since I was a kid in the 1970s, and it is definitely a younger man's game at the highest levels. That is especially true in singles play, and I think it's because tennis is really a running game. You really have to be able to run the ball down and that just gets harder as we age.
Oldest tennis players to win at the U.S. Open (Men)
Oldest man to win singles title at U.S. Open
The oldest man to win a U.S. Open singles title is Bill Larned, who was 38 years, 8 months and 3 days old when he won the title in 1911. Up until 1911, the U.S. Open operated under a challenge round system, whereby the previous year's winner did not have to play until the championship match. Larned won in 1910, so he didn't have to play again until the championship match in 1911.
The oldest man to win the U.S. Open after the challenge round system ended is Bill Tilden, who was 36 years, 7 months and 4 days old when he won the last of his seven U.S. Open singles titles in 1929. Tilden, however, played when only amateurs were allowed to compete. Professionals were not allowed to play in the U.S. Open until 1968, when the Open Era began.
The oldest man to win a U.S. Open singles title since the Open Era began is Australian Ken Rosewall, who was 35 years, 10 months and 11 days old when he won in 1970. Rosewall defeated fellow Aussie Tony Roche by a score of 2-6, 6-4, 7-6, 6-3 to win the title in 1970.
Oldest man to win his first U.S. Open singles title
The oldest man to win for the first time at the U.S. Open is Vic Seixas, who was 31 years and 7 days old when he won the singles title in 1954. Ken Rosewall, Bill Tilden and Bill Larned, all listed above, had all previously won the U.S. Open before they set the records as the oldest men to win a singles title at the U.S. Open.
Oldest male doubles champion at U.S. Open
The oldest man to win a doubles title at the U.S. Open is Australian Bob Hewitt, who was 37 years and 243 days old when he team ed up with fellow Aussie Frew McMillan to defeat Brian Gottfried and Raul Ramirez, 6-4, 6-0 in 1977.
Oldest male to win a mixed doubles title at U.S. Open
The oldest man to win a mixed doubles title is also Bob Hewitt. Hewitt was 39 years and 8 months old when he teamed with Greer Stevens to defeat Frew McMillan and Betty Stove for the 1979 title.