The novel says at one point that Mabel Werts "was the town" (3.423). But in fact the person who seems to most nearly encapsulate 'Salem's Lot, or at least the good parts of 'Salem's Lot, is not the widow, but the bachelor, Matt Burke.
Matt's taught at the high school for decades, and he's got a personal connection to just about everyone in the Lot, from Susan Norton, "who used to write such well-organized themes" (11.36), to Jackie Talbott, the bar waitress who is "a trifle scandalized" to see her teacher drinking with Weasel Craig (5.180), to Ruthie Crockett.
Matt doesn't just know everybody; he cares about everybody in town, in a way that Mabel Werts (for one) certainly doesn't. The one thing that upsets him, the novel says, is "the miserable ends some of his students came to" (7.121).
Matt's the only person who notices, and cares, that Mike Ryerson, his former student, is a mess. And he takes Mike home with him, even after he's pretty much figured out that Mike's being sucked on by a vampire, because he wants to protect him. With no kids of his own, Matt's a father to everyone. Jimmy Cody even compares him to Van Helsing (14.154), the fierce, wise vampire-hunter who saves the day in Bram Stoker's Dracula.
Alas, Matt's town, for all his love, chooses a darker father. The Master, Barlow, takes Mike Ryerson, and Ruthie Crockett, and Weasel Craig, and all the rest of the people Matt loves. Mike's final words to Matt—"I will see you sleep like the dead, teacher" (9.238)—are a threat, but they're also a rejection. Mike refers to Matt as "teacher"—it's his teacher he's going to kill, his mentor figure who will be corrupted. It's Matt as father and teacher that Mike intends to destroy.
Matt fights back, and the fight for him becomes almost a personal struggle between himself and Barlow. "My town is disintegrating almost before my eyes and you want me to sleep?" he tells Jimmy and Ben (14.600).
In the end, though, Matt loses. The Lot dies—"No one pronounced 'Salem's Lot dead on the morning of October 6" (14.6)—and Matt's heart stops not long after. His heart attack comes while he's talking to a former student whose name he can't remember, "Herbert-or-Harold," (14.950)—a stand-in for all his students, so pretty much a stand-in for the entire town.
Matt's last thought is, "Watch that last step, it's a killer" (14.957). He's thinking of his own death, but it can also be read as a warning to Jimmy, who dies when the vampires booby-trap the stairs in Eva's boarding house. Matt's still trying to save the town and his friends. He goes down fighting.