The city in the Southwest known as the "Gateway to the Desert" is Tucson.

Tucson, Arizona, is often referred to as the "Gateway to the Desert" due to its proximity to the Sonoran Desert and its role as a starting point for exploring the surrounding desert landscapes. The city is known for its desert beauty, unique flora like saguaro cacti, and its location near several national parks and natural reserves, making it a popular entry point for visitors to the desert region.