Complex sentence: The Museo Alameda is the largest Latino museum in the U.S. and the first formal Smithsonian affiliate outside of Washington D.C., located in the historic Market Square in downtown San Antonio, Texas.
Split into simpler sentences: The Museo Alameda is the largest Latino museum in the U.S. and one of the first museums to join the (Smithsonian) Affiliations program. Located in the historic Market Square in downtown San Antonio, Texas.