Jackson, Wyoming is the home of Tommy's community and covers both the town and the wider Jackson County, including the hydroelectric dam and the Hidden Pines Corral ranch. You visit it twice: in Tommy's Dam and in the short closing chapter, Jackson. It is the one safe, working settlement in Part I.
Joel and Ellie expect to find the town but come across the dam first, where Tommy and a crew are fixing a broken turbine. Maria and her riflemen meet you at the gate. After a bandit attack on the plant, Ellie rides off on a horse, and Joel and Tommy chase her across bandit country to an abandoned ranch house.
The last chapter puts you in control of Ellie as the car is blocked and the pair walk through the woods to an overlook above the settlement.
At the overlook Ellie admits her guilt over Riley, Tess and Sam, then asks Joel to swear that his account of the hospital is true. He swears, and she accepts it with a quiet okay. That exchange closes the game.
Boston
Boston, Massachusetts is the first region after the time skip and the city where Ellie grew up. You play The Quarantine Zone and The Outskirts here, and Left Behind's flashbacks with Riley take place in the same city. FEDRA holds the North End as one of the last working quarantine zones in the country.
Pittsburgh
Pittsburgh, Pennsylvania is a former quarantine zone now run by hunters who ambush anyone passing through. Joel and Ellie spend two chapters here, Pittsburgh and The Suburbs, and meet the brothers Henry and Sam. Expect heavy human combat and the largest pile of collectibles in the game.
Boulder
Boulder, Colorado is where Joel and Ellie search the University of Eastern Colorado for the Fireflies in The University chapter. Left Behind's present-day story picks up nearby at the Colorado Mountain Plaza mall, so this region covers both the campus and the mall.
Lincoln
Lincoln is a small Massachusetts town a few miles from Boston and the setting of Bill's Town, the fourth chapter. Joel and Ellie come here to call in a favor from Bill, a paranoid survivor who has rigged the whole town with traps, because they need a working vehicle.