The federal post office and former courthouse on Calle McKinley is one of the finest pieces of public architecture in Mayagüez. Built in the late 1930s in a stripped neoclassical style — a federal WPA-era project — it has a clean limestone façade, a deep colonnaded entry, and a marble lobby that still functions as the city's main post office.
Walk in if you need stamps. Otherwise the building is worth a slow look from the outside: the kind of confident civic structure that nobody builds any more.