Which NASA program sent the first American astronauts into orbit during the Space Race?

Project Mercury sent the first American astronauts into orbit during the Space Race.

NASA operated the programme from 1958 to 1963, aiming to determine whether humans could survive and function during orbital spaceflight. Its astronauts became known as the Mercury Seven, selected in 1959 from military test pilots with demanding flight experience.

Alan Shepard became the first American in space during a suborbital flight on 5 May 1961. John Glenn became the first American to orbit Earth on 20 February 1962, completing three orbits aboard Friendship 7. The programme ended after six crewed orbital missions.

Project Gemini came next and developed techniques such as spacewalks, orbital rendezvous, and longer missions. Apollo then used those capabilities for lunar expeditions, culminating in the first Moon landing in 1969.