Which space program enabled the first two-person flight in US history?

The Gemini program was pivotal in advancing human spaceflight and is recognized for achieving the first two-person flights in U.S. history. It was designed to develop and test techniques necessary for long-duration space missions and included a series of spaceflights that demonstrated critical technologies such as space rendezvous and docking. Gemini 3, the first flight of the Gemini program, launched in March 1965, successfully carried astronauts Gus Grissom and John Young into orbit, thus marking a significant milestone in U.S. space exploration.

Other options do represent important aspects of space exploration but are not directly related to two-person flights in the same manner as Gemini. The TRANSIT program was primarily concerned with satellite navigation, while the Apollo program focused on lunar missions, typically involving three astronauts. Salyut refers to a series of Soviet space stations, which, while historically significant, do not pertain to U.S. human space flight. Therefore, the Gemini program stands out as the specific program that enabled the first two-person flights in U.S. history, highlighting its role in the broader context of human space exploration.