It is Chicago’s answer to the Brooklyn brownstone, the Georgetown row house, and the London townhome. Except the two-flat remains affordable, still performing the duty to which it was first called in the early 20th century—that is, serving as both shelter and source of rental income for striving families moving up from cramped quarters. Though mass-produced, its bones—blocky yet graceful, with heavy cornice lines—are noble, descending from the Italian Renaissance palazzi. The sturdy brick façade, the bay windows, the enclosed porch, the narrow footprint: Call it the workingman’s palace.