Although it wasn't until the late 1930s and early 40s that the helicopter really took off, the decades before saw many experimentalists trying to get rotary flying machines off the ground. Emile and Henry Berliner, father and son, were the first Americans to make significant process towards this goal. Emile was already pursuing helicopter concepts while the Wright brothers were experimenting at Kitty Hawk, and in fact came up with the idea of counteracting the torque of the main rotor with a vertically mounted tail rotor. His son soon came to help, and suggested adding triplane wings so the aircraft could land if the rotor failed. The 1924 Berliner Helicopter was able to reach an altitude of 15 feet in a one-minute, 35 second flight. You can see it on display at the College Park Aviation Museum in Maryland.