Short answers, pulled from the story.
Project Mercury was the first U.S. human spaceflight program, running from 1958 through 1963. Its goal was to put an American astronaut into Earth orbit and return him safely, ideally before the Soviet Union achieved the same.
NASA announced the Mercury Seven on the 9th of April 1959: Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, Alan Shepard, and Deke Slayton. They were all active duty military test pilots selected from an original pool of 508 candidates.
Alan Shepard became the first American in space on the 5th of May 1961, flying a 15 minute and 28 second suborbital flight aboard Freedom 7. This came three weeks after Soviet cosmonaut Yuri Gagarin completed the first human orbital flight on the 12th of April 1961.
John Glenn became the first American to orbit Earth on the 20th of February 1962, flying Friendship 7 on a Mercury-Atlas mission. He completed three orbits, manually controlling the spacecraft after the automatic attitude control system failed.
McDonnell Aircraft Corporation was awarded the prime spacecraft contract in January 1959 and produced the capsules at its facility in St. Louis, Missouri. The spacecraft was designed by Maxime Faget and had close to 600 subcontractors.
Deke Slayton was grounded in 1962 due to a heart condition before he could fly a Mercury mission. He remained with NASA, became senior manager of the Astronaut Office, and eventually flew in space in 1975 as docking module pilot on the Apollo-Soyuz Test Project.