The 121st FS started receiving their F-16s in September of 1989. These were block 5 and 10 models coming from various regular USAF units converting to more modern C/D models. In the late eighties and early nineties it was still a habit to transfer older aircraft types to the ANG with the regular USAF units receiving all the latest hardware. The main task of the unit was air defense and attack. Neither role the squadrons block 5 and 10 models were set out to do. In the air defense role these models lacked any BVR capability, limiting them only to close range combat with their gun and Sidewinder missiles. In the attack role these airframes were able to deploy bombs, but with their smaller stabs the center of gravity of these aircraft was far from ideal making it quite a challenge for the pilots to fly these missions.
In 1994 this all changed with the introduction of newer small inlet block 30 models. The mission of the squadron remained unchanged, albeit their airframes were better suited to fly these missions. A BVR capacity became available and with the more modern APG-68 radar and other electronics these airframes are better suited for the attack role as well.

District of Columbia ANG (121st TFS) F-16A over Washington D.C. [Photo by Keith Jasons]
After the events of September 11th, 2001 the squadron took on an Air Sovereignty Alert Detachment role, stationing a number of airframes at air force bases around the country to fly alert missions. During one of those missions, on May 11, 2005 the squadron scrambled to intercept an aircraft that wandered into the no-fly zone around the White House. Customs officials had also scrambled a Black Hawk helicopter and a Cessna Citation jet at 11:47 a.m. to intercept the plane. The Customs aircraft gave way when the F-16s arrived flew on the wing tips of the little plane. They dipped their wings - a pilot's signal to ‘follow me’ - and tried to raise the pilot on the radio. But the Cessna didn't change course and it was flying too slow for the F-16s. The frustrated pilots had to take turns dropping flares, breaking away and returning to drop more flares. One senior Bush administration counterterrorism official said it was ‘a real finger-biting period’ because they came very close to ordering a shot against a general aircraft. Finally, when the Cessna came within three miles of the White House - just a few minutes flying time - it altered course.
On May 6, 2008 the squadron flew it's 2000 scramble since the events of September 11, 2012. Most scrambles do not lead to such stories as noted above.
The most recent change within the unit happened in 2010 when the squadrons airframes were exchanged for big mouth block 30 models coming from the 188th FS. The first airframe to arrive (#87-0227) touched down at Andrews on April 1st, 2010.

Maj. Scott Arbogast, of the 113th Wing, taxies F-16D block 30
#85-1509 from the 121st FS at Andrews
AFB on January 17th, 2008. [USAF photo by SrA. Renae L. Kleckner]