Preston Garvey is a senior officer of the Commonwealth Minutemen, a volunteer defense militia operating in the Commonwealth in 2287. He is also available as a companion of the Sole Survivor.

Preston Garvey originally enrolled with the Minutemen under Colonel Hollis at the age of seventeen. An avid believer in the espoused justice of the Minutemen cause, Preston rose through their ranks to become an officer under the direct command of Hollis himself. Things began to change for the worse when settlements under the protection of the Minutemen grew complacent. Freed from the greater concerns of the erstwhile dangers of the Commonwealth, settlements increasingly neglected their obligations to the collective in favor of petty self-interests.

In 2287, Sturges, an inhabitant of the influential trading hub at Quincy - requested the aid of the Minutemen after having heard one of Mama Murphy’s visions, which foresaw the town being surrounded and massacred. Although the majority saw Murphy as burned-out chem addict, Sturges went behind his fellow citizens to invoke the protection of the Minutemen. Preston joined Hollis on a mission to rescue Quincy, where they found the Gunners besieging the town.

The Minutemen dispersed the Gunner lines and were welcomed by the citizens of Quincy while the Gunners temporarily retreated. The Minutemen quickly moved to fortify the town, but their efforts proved insufficient as in the northwestern part of the town, the Gunners reformed their lines and relentlessly probed the town's defenses for weaknesses[citation needed]. An ex-Minutemen officer named Clint had revealed himself to Colonel Hollis as the leader of the invading force. Hollis felt extreme anger at this betrayal. The citizens expressed confusion and frustration. Clint sought to establish terms of surrender for Quincy and its defenders; these terms were summarily rejected by Hollis.

While the subsequent events are not explicitly recorded in text, the outcome for the Minutemen is broadly established by dialogue with Preston and various other wastelanders: the Minutemen requested support, which did not arrive; the Gunners overwhelmed the defenders and murdered nearly all of the civilians; Col. Hollis, the linchpin of the long-dwindling Minutemen cause, died fighting. The event is known as the Quincy Massacre and it catalyzed the disintegration of the remaining settlements under Minutemen protection.

Consequently, Preston gathered the few remaining Quincy civilians and loyal Minutemen and fled, several of the refugees lost their live to the hands of the Gunners, before the group shook their pursuit at Jamaica Plain. The refugees next moved to Lexington. Regrettably, as Preston testifies, Lexington was filled with feral ghouls; the hardships of the town gradually whittled the group's numbers down to just over ten. Eventually the group moved to Concord where they took shelter in the Museum of Freedom, only to find themselves under the constant predation of raiders, who unbeknownst to the group are under orders from their leader Jared, to acquire Mama Murphy.

By the time the Sole Survivor arrives to help Preston, he is leading the last pocket of of people under the protection of the Minutemen. His group numbers only five - a mere fraction of the original twenty who escaped Quincy under his guidance.