This confluence provides water for Tumacácori and Tubac and collects in the marsh lands around San Xavier del Bac downstream, to the north.

Harshaw Creek drains the area between the Patagonia Mountains to the west and the high San Rafael Valley grasslands to the east.

Sonoita Creek contains black bullhead, red shiner, mosquitofish, crayfish, American bullfrogs, largemouth bass, Gila topminnows, speckled dace, longfin dace, Sonora suckers, and desert suckers.

The route ran from a connection with the Southern Pacific Railroad in Benson, then south to Fairbank (about 13 km or 8 miles west of Tombstone) then west to Sonoita – Patagonia and Rio Rico, then south to Nogales.

Only 15.74 km (9.78 mi) of track remains in place today, from Rio Rico to Nogales, and is operated by the Union Pacific Railroad.