Coronado National Memorial was set aside to commemorate the expedition of Francisco Vásquez de Coronado. The spectacular view, of Mexico and the San Pedro River valley, believed to have been the route taken by the expedition, was the primary reason for the memorial's location in Montezuma Canyon. On a clear day, visitors can see Baboquivari Peak, over 80 miles west of the Montezuma Pass overlook. Generally, air quality is best in late fall and early winter, when there is little dust and smoke and low humidity. In the spring, when roads and fields are dry and dusty, gusty winds often bring a hazy shroud over the San Pedro River valley, obscuring views to the east. Early summer fires from as far away as southern Mexico and Texas can also cause a layer of smoke to hang in the air. Since the smelter at Cananea, Sonora, located about 15 miles south of the memorial in Mexico, closed several years ago, air quality has improved, however there are plans for construction of nearby power plants along the border.