According to various pages online, this represents:

July 3, 1863, the brave men of the 1st Maryland emerge from the wood line into a wall of musketry on Culp's Hill at Gettysburg.

aka

the 1st Maryland Battalion CS attack on Union fortifications on Culp’s Hill.

It's a little confusing because both sides had a "1st Maryland" unit at Gettysburg, and the Confederate 1st Maryland was renamed (and is often called) the 2nd Maryland. I think the relevant wikipedia page is here:

https://en.wikipedia.org/wiki/2nd_Maryland_Infantry_Regiment_(Confederate)#Battle_of_Gettysburg

Johnson's division, including the 1st Maryland, arrived at Gettysburg late in the afternoon on July 1, 1863, taking position on the far edge of the Confederate left at the foot of Culp's Hill; the men were exhausted after a 130-mile forced march.[4] Culp's Hill was a rocky wooded hill topped by a line of well fortified enemy breastworks.

On July 2 the Confederates attacked the hill, with the 1st Maryland, the 10th, 23rd and 37th Virginia regiments, and 3rd North Carolina regiment, all assaulting the Union breastworks, defended by General George S. Greene's 12th Corps. The Marylanders and others were initially able to breach the works and drive out Green's men, and they held their position until the next morning, July 3.

The morning of July 3 revealed the full scale of the Union defenses, as enemy artillery opened fire at a distance of 500 yards with a "terrific and galling fire", followed by a ferocious assault on the Marylander's position.[4] The result was a "terrible slaughter" of the Third Brigade, which fought for many hours without relief, exhausting their ammunition, but successfully holding their position.[4] Then, late on the morning of July 3, General Johnson ordered a bayonet charge against the well-fortified enemy lines. Steuart was appalled, and was strongly critical of the attack, but direct orders could not be disobeyed.[9] The Third Brigade attempted several times to wrest control of Culp's Hill, a vital part of the Union Army defensive line, and the result was a "slaughterpen",[4] as the First Maryland and the Third North Carolina regiments courageously charged a well-defended position strongly held by three brigades, a few reaching within twenty paces of the enemy lines.[4] So severe were the casualties among his men that Steuart is said to have broken down and wept, wringing his hands and crying "my poor boys".[8] Overall, the failed attack on Culp's Hill cost Johnson's division almost 2,000 men, of which 700 were accounted for by Steuart's brigade alone—far more than any other brigade in the division. At Hagerstown, on the 8th July, out of a pre-battle strength of 2,200, just 1,200 men reported for duty.[4] The casualty rate among the First Maryland and Third North Carolina was between one half and two-thirds, in the space of just ten hours.[2][4]