In 1842, young men in Detroit secretly delivered their valentines by hand, as the U.S. Postal Service had not yet set up shop in Detroit. Detroiter John Webb Chester recalled those days when he was interviewed in his 90s by the Detroit Free Press in 1914: “Oh, of course we used to send them. All the boys did. … We would go to a house where the girl of our choice lived, stick our valentines under the door, and then disappear as fast as ever we could.”
Source : Bill Loomis, “Valentine’s Day history: When Feb. 14 meant tender effusions (but no spooning!)”, Detroit News, February 12, 2014.