John Reynolds played a role in this too. Buford’s cavalry was the true vanguard, though Reynolds was in command of the advance corps (Meade’s various corps were all strung out at this point and not unified in preparation for a battle). His orders were explicit not to bring on a general engagement, which made sense given the state of his army. Meade also wanted to fight back at Pipe Creek, some 20 miles southeast, and had issued orders to ultimately draw his army together there. To fight in Gettysburg would mean issuing all new orders to generals who were many miles in many directions. There was uncertainty of where Lee’s forces were in PA, and the belief was they would try to attack Washington from the NW, so it made sense not to advance too far north.

Reynolds clearly understood that Gettysburg had favorable terrain and ordered Oliver Howard’s corps to join him there, rather than fall back to Pipe Creek. After Reynolds was killed and Winfield Hancock arrived at Gettysburg, he confirmed Reynold’s decision to fight there rather than fall back. That was good enough for Meade, who abandoned the Pipe Creek line and moved up to Gettysburg.

It’s worth noting that a similar process was happening to Lee’s army. Buford had engaged Devin’s brigade (Hill’s corps), which was the vanguard of the Army of Northern Virginia. Lee had to quickly bring his three corps together at Gettysburg. Both he and Meade benefitted from the many, many roads that led to Gettysburg like the spokes of a wheel.