We saw this placard on our way home (we live in Gainesville, which abuts the Manassas battlefields to the West), and thought we should share it with you. Thanks to the Prince William County Historical Commission for putting it up in 2017.
It is mostly self-explanatory. The key points are that the railroad for which Gaines sold the rights on his land along the Warrenton Turnpike (today’s Lee Highway, Rt. 29) — with the specification that it be named after him, i.e. Gainesville — was the one used by Joe Johnston at First Manassas. Their arrival helped turn the tide against the Union that day.
Also, undoubtedly, Lee and Longstreet and their men passed over this land during Second Manassas — the advance that General John Pope refused to believe existed until it was too late.
I researched this question, but found no answer: perhaps my readers can. Note that Gaines’s middle name was Brawner and the Brawner Farm on the Second Manassas battlefield saw considerable fighting. One source says the Brawner’s on that farm were in fact tenant farmers and the farm was owned by the Douglas family. Were the two Brawners related?