Buckley is the dog at Tommy's hydroelectric dam in Jackson County. You meet him in Tommy's Dam outside the generator building as Tommy walks Joel to his office, and Joel can stop to pet him.
During Tommy's Dam, follow Tommy toward his office. Buckley waits outside the generator building, and the prompt to pet him appears as you walk past.
Every other dog you meet in Boston and Pittsburgh is trained to hunt you down. A friendly dog at the dam is a small sign that Tommy's people live more peacefully than anyone else on the trip.
Buckley turns up during the tour Tommy gives Joel after the reunion at the gate. The same stretch of Hydroelectric Dam holds the Smoke: Chemistry training manual by the control panel in the dam's control room and Oliverio's Firefly pendant in a cabinet in the back room down the stairs from it, and later the workers get the generator running again.
Maria Miller
Maria Miller is Tommy's wife and the leader of the settlement in Jackson, Wyoming. You meet her at the hydroelectric dam in Tommy's Dam, where she first holds Joel and Ellie at gunpoint before learning Joel is her brother-in-law.
Seth
Seth is a Jackson resident on guard duty at the hydroelectric dam in Tommy's Dam. He is the man beside Tommy on the wall, rifle trained on Joel and Ellie, when they first reach the gate.
Tommy Miller
Tommy Miller is Joel's younger brother, a former Firefly who now helps run the settlement at Jackson, Wyoming. He drives Joel and Sarah through the chaos of the prologue, and twenty years later Joel tracks him down at a hydroelectric dam in the chapter Tommy's Dam, hoping he will take Ellie to the Fireflies.
Callus
Callus is the horse Joel and Ellie ride from Jackson County to the University of Eastern Colorado and beyond. He first carries Joel when Ellie runs off in Tommy's Dam, and Ellie names him on the road to the university.