Tucson is a proper noun. Tucson is (1) a city in southeastern Arizona ringed by mountain ranges; long known as a winter and health resort but the population shift from industrial states to the Sunbelt resulted in rapid growth late in the 20th century.
The following articles provide more information about the proper noun Tucson.
With about 350 days of sunshine each year, Tucson, Arizona is a popular vacation destination. This website, published by the Metropolitan Tucson Convention & Visitors Bureau, includes trip planning information about hotels, events, restaurants, activities, and attractions.