The Freedom Trail starts here! Visit this once-idyllic park surrounded by ancient architectural prewar mansions and the remains of the State House, but be warned; there are numerous signs recommending you stay away from the pond at the park’s west end. Perhaps it’s better to start investigating the thin red line still visible along much of the sidewalks, a trail leading you through some of the most famous historical structures still (partly) standing. Surrounded by five other neighborhoods, Boston Common is at the nexus of the city south of the river.”— Fallout 4 Vault Dweller's Survival Guide
Boston Common consists of a large and open, but irradiated area. The common contains a few other locations, such as the Massachusetts State House to the north, Swan's Pond to the western side of the green, the Boylston Club - the red door in the southern row of buildings off of the common, the Prost bar - which is a basement bar on the north corner of the western row of buildings, and Park Street station which is located at the north-easternmost corner of the common.
The Freedom Trail also begins at Boston Common. There's a friendly protectron named tour bot located on the eastern side of the common next to the fountain. In front of the fountain there is a sign and a seal. The sign reads: "At Journey's End Follow Freedom's Lantern". The seal says "The Freedom Trail. Boston." But there appears to be a code. The number 7 is written in the center with red ink, and the letter A in Trail is bracketed. Each of the seals has a number that corresponds to a letter in "Railroad" - for example the seal marked 1 has the "R" indicated.
- Grognak the Barbarian issue #6 (+5% unarmed or melee critical damage) - On the ground in the gazebo at the center of the common next to a skeleton and (severe) radiation barrels.
The Boston Common only appears in Fallout 4.