The Bunker Hill Monument was erected to commemorate the Battle of Bunker Hill, the first major conflict between British and Patriot forces in the American Revolutionary War on June 17, 1775. The 221-foot (67 meter) granite obelisk was erected on the site of this battle between 1827 and 1843, and an exhibit lodge built adjacent to the monument in the late 19th century houses an exposition dedicated to the exhibit. After the War, it became a fortified settlement, well defended, and surrounded by a thick defensive wall. In the declining era of the Minutemen the settlement was once wiped out by raiders.
By 2287, Bunker Hill is a major trading hub for the Commonwealth, located in the middle of everywhere. It worked with the Minutemen while they were still operational, but was left vulnerable when the faction unraveled due to infighting and competition. After a disastrous few years, the Hill finally made a deal with the local raiders. In return for paying a hefty tribute, the raiders leave the Hill and most of the traders coming to visit in peace.
The sheer number of people and the relative security of the settlement made it an excellent location for use as a safehouse by the Railroad. Operated by Old Man Stockton, the Hill's Railroad operation takes care of many synths. However, it takes only a single miscalculation for it to attract the attention of the Brotherhood and the Institute.
Bunker Hill is only accessible as a settlement after completing The Battle of Bunker Hill. The entire settlement is very well protected, only accessible from the south and east gates, but lacks defensive emplacements. As such, defending the settlement is rather easy, which is especially fortunate since it is regularly attacked. Additionally, the settlement is already well established in terms of structures, and has lots of land one can develop for agriculture and water collection.
The settlement is centered around the memorial to the Battle of Bunker Hill, with the cracked-open lodge serving as bazaar and the obelisk as a look-out point. Shacks that contain living quarters, outhouses, and additional stores (including Kay's clinic and the Savoldi's common house) surround the building, clinging to the walls. The settlement workshop is within Kay's clinic. Utility basement
↑Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.423-425: "[8.02] BUNKER HILL This large granite monument was erected to commemorate the Battle of Bunker Hill, which was the first main confrontation with the British back in 1775 during the American Revolutionary War. Today it serves as a reasonably well-defended settlement. The Railroad currently uses it as a pickup point for escaped synths, who are met and hidden by a local sympathizer until a Railroad agent can take them to safety.  Entrance And Obelisk This imposing landmark was erected between 1827 and 1843 using granite from quarries in Quincy" (Fallout 4 Vault Dweller's Survival Guide Map)
↑The Sole Survivor: "What's your opinion of Bunker Hill?" Deb: "Well, it's nice enough. Grew up with the caravans, so I feel right at home here. Don't like how we have to pay Raiders protection money, but that's the cost of doing business in the middle of everywhere." (Deb's dialogue)