Captain America's motorcycle was a 1942 Harley-Davidson WLA "Liberator" with custom additions made for the personal use of Captain America during his service in World War II. It began as a standard Harley-Davidson model motorcycle that was modified by Howard Stark, who added several weapons and gadgets for use in combat situations.
Near the end of the war, in a plan to infiltrate HYDRA Headquarters, Captain America used this motorcycle to attack the base head-on. The bike's gadgets proved useful in taking out a squadron of HYDRA soldiers on motorbikes patrolling the outside of the base. As Rogers approached the base, he used the motorcycle to jump the main wall. He abandoned the bike after setting it to self destruct, aiming the bike for the base's main blast doors, which were taken out by the resulting explosion.
In Captain America: The Winter Soldier, a replica of Captain America's World War II-era motorcycle was put on display at the Smithsonian Institution in Washington, D.C., alongside other displays documenting the activities of Captain America.