The University of Eastern Colorado is the Boulder campus where Joel and Ellie expect to find the Fireflies in The University chapter. You search it on horseback and on foot through the Go Big Horns and Science Building sections, and it holds 17 collectibles.
Survivors barricaded themselves in parts of the campus and waited almost a year for rescue, scavenging in Boulder. Newspaper clippings they brought back showed nobody was coming.
The Fireflies later ran a research lab in the science building, using monkeys as test subjects. They pulled out as infected overran the perimeter, and a scientist bitten by an escaped monkey left a final recording.
Joel starts generators to open gates while Ellie waits with the horse, then the pair learn the Fireflies have moved to Saint Mary's Hospital in Salt Lake City. Hostile survivors attack, and Joel is badly hurt on rebar before Ellie gets them both out.
Colorado Mountain Plaza
Colorado Mountain Plaza is the snowbound mall near Boulder where Ellie hunts for medical supplies in Left Behind's present-day chapters. You play Back in a Flash, So Close and The Enemy of My Enemy here, fighting both infected and hostile survivors.
Silver Lake
Silver Lake is a snowbound Colorado resort town and the setting of the Lakeside Resort chapter, where Ellie is playable for most of the winter. A group led by David lives here. Its surroundings include an abandoned coal mine and the Whitefish Lake rest area.
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.