After being postponed from an earlier date (which resulted in the Russians beating the United States into space) the launch countdown for Freedom 7 began at 8:30am EST on May 4, 1961.

All operations went smoothly and were completed ahead of schedule. A built-in hold of approximately 15 hours was called at T-6 hours 30 minutes in order to install the various pyrotechnics into the spacecraft. The hydrogen peroxide system was serviced and the launch crew was given time to rest before the final countdown. The countdown was resumed at 11:30pm EST on May 4.

Another built-in hold of 1 hour was initiated at T-2 hours 20 minutes. This hold was to assure that spacecraft preparations had been completed before the astronaut was transported to the pad. After only a few minor delays, Shepard was transported to the Pad and the countdown resumed and continued until T-15 minutes. At this time it was determined that photographic coverage of the launch and flight could not be obtained because of low clouds near the launch area.

Weather forecasters predicted that visibility would improve rapidly within 20 to 45 min. During this time, one of the 400hz power inverters to the launch vehicle had regulation problems. The count was recycled to the T-35 minute and holding mark and the count picked up 86 minutes later after the replacement of the inverter.

Again at T-15 minutes it was necessary to hold the count again to make a final check of the real-time trajectory computer. The countdown then picked up and proceeded until liftoff.

After a short but successful flight the capsule splashed down in the Atlantic Ocean at 75deg 53min longitude, 27deg 13.7min latitude.

Source: NASA Human Spaceflight