Good question. Hoping to learn more from other answers.

The Eastern Shore was pretty much Union for the whole war, but full of Confederate sympathizers. Harriet Tubman was from there and the Underground Railroad had to be “underground,” even in Maryland.

Maryland was complicated. It was prevented from joining the Confederacy, which is not the same as joining the Union. Many were sympathetic to the Confederacy but saw their economic and political fortunes in the Union.

Virginia’s Eastern Shore actually sided with the Union, for the most part. Prior to the war, the two counties voted against secession in Richmond but ultimately did not oppose the Ordnance. Their solidarity did not last, however. The almost immediate break with Richmond was led by the Chincoteague Islanders who depended on northern markets for their oysters and fish—an industry that was vital to the area and also required no slaves. But, there were tensions, which came to a head at the Battle of Cockle Creek, a minor skirmish by the standards of the time and easy Union victory.

After that the Union kept a ship and 4,000 troops at Chincoteague for the balance of the war.

There were the “Shore Runners” who smuggled people and goods across the Bay. And there was martial law imposed later in the war to combat shore running, enforced by Union troops.

Eastern Shore planters did not have the wealth that mainland planters did. Their smaller plantations were limited in what they could produce. And with the high number of free Blacks in the area, they felt the need to be especially harsh to keep their slaves enslaved. The planters did not have the economic clout that the fishermen had. (One way some Eastern Shore planters earned extra income was to be slave breakers. People would send “difficult” slaves there to be broken. Frederick Douglass was enslaved on one of those plantations, in Talbot County.). The political leanings were southward, but the economic reality looked northward.

So the whole region was teetering on the edge between the two sides as tensions were developing before the war.

Once war broke out, the Union acted swiftly to protect the entrance to the Bay. And the Battle of Cockle Creek secured the Eastern Shore. That took the Eastern Shore off the military map, as it were.

So when the Eastern Shore counties of Virginia went Union, Richmond was little able to do anything about it. The Confederacy had more pressing issues.

Yet, men did volunteer and mustered a Virginia regiment that served on the Mainland. Marylanders also mustered, but a Union regiment. And, the Union also mustered a regiment of US Colored Troops.

Ed:sp