Los Angeles ? For the 368th and last time, the United States launched a Titan rocket into space Wednesday.

The blastoff of the 16-story, unmanned Titan IV signaled the end of an era that began in 1961, as the U.S. military converts to cheaper space boosters.

The last Titan carried a secret payload for the National Reconnaissance Office, which oversees the nation’s spy satellites.

Titan’s past included many high-profile missions, including boosting Gemini manned spacecraft into orbit in the mid-1960s as preparation for the Apollo moon landings.

The workhorse rocket, originally designed as a weapon-bearing intercontinental ballistic missile for the Cold War, also sent many scientific crafts on their way to Mercury, Mars and the outer planets.

About 3,000 spectators and military dignitaries gathered at Vandenberg Air Force Base, north of Los Angeles, to watch Wednesday’s historic launch.