Modestly produced but rich in feeling, this documentary follows 56-year-old Wendell Watkins, a Detroit mail carrier for 26 years, as he walks his longtime delivery route and chats with folks along the way. His route ranges from well-kept homes to bombed-out wrecks, which enables director Pam Sporn, drawing on a cornucopia of historical photos, to turn her movie into a potent history of racial and economic change in the Motor City—from the Great Migration that brought Watkins’s parents up from the south to the poverty and inequality that fed the 1967 rioting to the cold-hearted real estate speculation that helped gut black neighborhoods in the new century as the city veered toward bankruptcy. Watkins, whose retirement provides the movie’s denouement, is a smart, engaging tour guide with a sharp sense of social justice, and his sit-downs with various old-timers are relaxed, warm, and funny.