With today's last Space Shuttle flight, we've reached the end of an era in American space exploration. In this gallery, we look back on 30 years of the Space Shuttle program: the beauty of our space outposts, the engineering marvels of the Shuttles, and the brave sacrifices many people made to leave this gravity well. It's been a good run, NASA. A really good run.

Here you can see the first Space Shuttle, Enterprise, as it takes flight for the first time over the Dryden Flight Research Facility in 1977 (AP).

Space Shuttle Columbia at the Kennedy Launch Complex, 1980 (Flickr/State Archives of Florida)

Senator John Stennis celebrates a successful test of the Space Shuttle's main engine, October 1978 (Flickr/NASA)

Columbia, followed by a chase plane, as it lands at Edwards Air Force Base, April 1981 (AP)

Sally Ride, the first female American astronaut, speaking with ground control on the shuttle Challenger, June 1983

Astronaut Bruce McCandless II, approximately 300 feet from Challenger, as he takes the first untethered space walk in history, February 9, 1984 (AP)

Challenger explodes 73 seconds after liftoff, January 28th, 1986 (AP)

Reaction to the Challenger tragedy, Concord, New Hampshire, January 28th, 1986 (AP)

The robot arm of Discovery maneuvers the Hubble Space Telescope outside of the shuttle payload bay, 1990 (AP)

Endeavour captures the Wake Shield Facility, an experimental science platform, after it was caught in solar winds for two days in September 1995 (AP)

Space Shuttle Columbia as it journeys from the Vehicle Assembly unit to the launch pad at Kennedy Space Center, March 1998 (AP)

Senator John Glenn, Jr., returns to space as a a Payload Specialist aboard the shuttle Discovery, October 1998 (AP/NASA)

Columbia lands at the completion of a two million mile journey wherein the crew deployed the Chandra X-ray Observatory, July 1999 (Getty)

A picture of the crew of Columbia during mission STS-107, from a roll of undeveloped film found in the shuttle's debris, 2003 (AP/NASA)

Streaks in the sky as Space Shuttle Columbia disintegrates upon re-entry, February 1, 2003 (AP)

Discovery crew members, on the first shuttle flight in almost three years, conduct an in-flight repair of thermal tiles on the underside of the Discovery, August 2005 (AP)

Lifting Atlantis within the Vehicle Assembly Building at the Kennedy Space Center in preparation for a September launch, July 24, 2006 (AP)

Space Shuttle Atlantis leaves a streak of light as it passes overhead. Photo taken on September 20, 2006 in Tyler, Texas, where the initial disintegration of Columbia took place in 2003. (AP/Dr. Scott Lieberman)

Launch Control at Kennedy Space Center during an Atlantis launch, September 2006 (Flickr/NASA)

Atlantis lands at Cape Canaveral at the conclusion of a 12 day mission, September 21, 2006 (AP)

Atlantis prepares to dock with the International Space Station, June 2007 (AP)

The International Space Station as seen in the reflection of Astronaut Scott Parazynski's visor during a space walk outside of shuttle Discovery, October 30, 2007 (AP)

Image taken at Banana River viewing site near Kennedy Space Center as Discovery leaves a trail after launch, 2009 (Flickr/NASA)

Atlantis departs for the final servicing of the Hubble Space Telescope, May 2009 (AP)

One of the personal effects taken aboard by Commander Mark Kelly, a baseball, floats in the cabin of Endeavour, May 2010 (AP)

Discovery en route to the International Space Station, August 2010 (Flickr/NASA)

Astronauts Mastracchio and Anderson in the payload of Discovery on a mission to perform maintenance work on the International Space System, 2010 (AP)

Memorial for Challenger crew member Ellison Onizuka, 2011 (AP)

Discovery, ready for its final mission, is rotated on the launch pad to expose the orbiter, February 2011 (AP)

Discovery, on its last mission, as the shuttle prepares to dock with the International Space Station, February 2011 (AP)

The crew of Atlantis is transported to a dress rehearsal for the final mission of NASA's Space Shuttle Program, March 2011 (AP)

Endeavour sits on the launch pad in April 2011 prior to its final launch in May 2011 (AP)

Atlantis moves from the Vertical Assembly Building to the launch pad in May of 2011 in preparation for a July launch (AP)

Mission Control at the Johnson Space Center in Houston during a simulation of the final Atlantis mission, 2011 (AP)

The sun, a portion of the International Space State, and Earth can be seen during a spacewalk taken on the last flight of Endeavour, May 27, 2011 (AP)

A view of Discovery's payload bay as it is being decommissioned and decontaminated in June 2011 (AP)

Hand made sign attached to a payload canister destined for the final flight of Atlantis, June 10, 2011 (AP)

Atlantis, as it sits on the launch pad on June 17, 2011 in preparation the Shuttle Program's final flight in July 2011, in which it will carry spare parts and supplies to the International Space Station (AP)