First introduced in 1885 by Amish farmers in Chester County, Pennsylvania. According to Carolyn Male, Tom Hauch at Heirloom Seeds in Pennsylvania was the first to get Red Brandywine out of the SSE Yearbook and offer it commercially. He sent seeds to Steve Miller at the Landis Museum in PA which features Amish varieties. Red Brandywine is the only one of the brandywines to have a documented Amish history and that's the one that Steve got when he followed up on the background. I have my seeds right from Steve to make sure they are the authentic ones
Here is a link with an extensive article on Brandywines by Craig Lehoullier.