Today is the 150th anniversary of the Battle of Gettysburg, arguably the most pivotal battle of the American Civil War. Naturally, the History Channel has commemorated the day with an "American Pickers" marathon.
On this first day is that Union cavalry soldiers were pushed back through the town of Gettysburg but were reinforced by Federal troops under General John Reynolds. Reynolds was killed early on and command passed to Oliver Howard who fought a defensive battle until the rest of the Federal army could arrive.
And here's one of those great "what if" moments in history: after a long march and a day of fighting, Robert E. Lee asked General Richard Ewell to take the heights south of Gettysburg "if practicable." A foothold on either Cemetery Hill or Culp's Hill would open up the battlefield for Confederate artillery and change the course of the battle. But Ewell deemed it impractical. His troops were tired, the landscape uncertain (and uphill), and he feared that his flank would be exposed to amassing Union troops.
Lee, who was accustomed to the aggressive style of Stonewall Jackson, was disappointed by Ewell's failure to press the Rebels' advantage. On the other hand, by leaving Ewell wiggle room in his order, Lee let this chance slip away. Union troops reinforced the high ground and the Confederates suffered terrible losses trying to gain a second opportunity.