Flagg, TexasFlagg is an unincorporated community in Castro County, Texas, United States. According to the Handbook of Texas, the community had an estimated population of 30 in 2000.GeographyFlagg is located at the intersection of Farm to [Market Road 1055|Farm to Market Roads 1055] and 1524, southeast of Dimmitt, east of Bovina, and south of Hereford in southwestern Castro County.EducationIn 1925, Flagg had a school and the school district was formally created four years later. The community joined the Dimmitt [Independent School District] in 1945.