Colonel Peter Lyle commanded the 90th Pennsylvania at the Battle of Antietam until he took over brigade command. Lieutenant Colonel William Leech then took over the regiment.

Two members of the regiment were awarded the Medal of Honor for their actions at Antietam. Lieutenant Hillary Beyer of Company H remained with the wounded when the rest of his company was forced to fall back, caring for them and carrying one to safety. Private William H. Paul of Company E picked up the flag when the color bearer and two members of the color guard were killed, and carried it through the rest of the battle.

From the monument:

Here fought the 90th Penna. (Phila) Sept. 17, 1862 A Hot Place

This monument is a reconstruction of the original that was created by the veterans of the regiment. It was made from three actual Civil War rifles, and was dismantled around 1930 due to its state of deterioration and fears of theft.

Gary Casteel of Four Winds Studio designed and sculpted the new monument, which was planned and funded by Descendants of the 90th Pennsylvania Volunteers. It was dedicated on the 142nd anniversary of the battle, September 17, 2004.

The 90th is also honored by three monuments on the Gettysburg battlefield.