The flag of Prince George's County, Maryland, as officially defined in the county code. What differentiates it from many currently-used flags is that it uses the 1958 to 1971 county seal in the top left-hand corner instead of the current post-1971 seal. Although it is not as widely used, according to the county code, as of 2018, this is still technically the official flag of the county: "Sec. 1-106.  County flag; contents. The official County flag shall be a three (3) feet by five (5) feet flag of white, divided in equal quadrants by four (4) inch stripes of red and containing in its upper left quadrant the official seal of the County as adopted by the Board of Commissioners on November 25, 1958. (Ord. and Res. 1967, Sec. 1-6)". However, in practice, most, if not all, of the flags manufactured and currently used by the county disregard the county code's description of the flag and instead feature the post-1971 seal in the top left-hand corner. More information about the flag and seal can be found here, here, here, and here.
https://web.archive.org/web/20161021161357/http://www.princegeorgescountymd.gov/documentcenter/view/16267
Prince George's County government