Garcia is an unincorporated community located in Costilla County, Colorado, United States. The San Luis post office serves Garcia postal addresses. Originally settled in 1849 as La Plaza de los Manzanares, Garcia rivals San Luis as the oldest continuously occupied settlement in Colorado. A post office called Garcia was established in 1915. The c…Garcia is an unincorporated community located in Costilla County, Colorado, United States. The San Luis post office serves Garcia postal addresses. Originally settled in 1849 as La Plaza de los Manzanares, Garcia rivals San Luis as the oldest continuously occupied settlement in Colorado. A post office called Garcia was established in 1915. The community was named for the local Garcia family.