May 13, 1861 - Occupation of Baltimore, MD by Federal Troops At first, President Abraham Lincoln complied with the Baltimore authorities request to reroute troops to Annapolis after the Baltimore Riots in April. On May 13, without permission from Army Headquarters, Brig. Gen. Benjamin F. Butler moved Union troops, including members of the 6th Massachusetts Regiment that was attacked in the riot on April 19, from Relay Station into Baltimore and took possession of Bunker Hill. He claimed that he had reports of a riot in the city and that upon entry into the city, he had martial law declared. Generally, this move was met with approval in the North. This act squelched most subsequent pro-Confederate activities.
The mayor, city council, and police commissioner, who were pro-South and seemingly incompetent at maintaining order in the situation, were arrested for their alleged participation in the riot and imprisoned at Fort McHenry. Suspected secessionists, including Francis Scott Key's grandson and a number of state legislators, were held without charges. Butler reported that he found several manufactories of arms, supplies, amd munitions meant for the "rebels."
After the occupation of the city, Union troops were garrisoned throughout the state. Several members of the Maryland legislature were arrested, and the state was placed under direct Federal administration. Days afterward, North Carolina became the final state to approve secession on May 21. Delaware was occupied by Union troops due to its proximity to (and to prevent a repeat of the events that took place in) Maryland. Union forces continued to maintain an occupying presence in Baltimore for the remainder of the war. Maryland would remain under the Federal administration, and Delaware occupied, until the end of the war.
May 24, 1861 - Occupation of Arlington Heights, VA by Federal Troops On May 24, before daylight, several Union regiments were ordered to cross the Potomac River and seize control of the port city of Alexandria. Col. Elmer E. Ellsworth was leading one of the Union regiments. Upon entering Alexandria, they did not face any resistance. While securing different points in the town, Ellsworth noticed a Confederate flag flying from the top of the Marshall House Hotel. Ellsworth went up to the roof and took down the flag. While he was going back down the stairwell, he was met by the hotel's innkeeper, James T. Jackson. Jackson shot Ellsworth with a shotgun and killed him. A nearby Union soldier, Pvt. Francis Brownell, was also fired at but missed him. He saw Jackson and immediatelly shot and killed him.
On April 24, after occupying Alexandria, Maj. Gen. Charles W. Sanford and his Union troops occupied the town of Arlington. At Arlington was the Custis-Lee mansion overlooking the Potomac River. Built by George W.P. Custis, adopted son of George Washington, it was then the residence of Custis' son-in-law, then Brig. Gen. Robert E. Lee of the Virginia state forces. Sanford made the home his headquarters in order to protect it from any possible future vandilism.
May 29, 1861 - Occupation of Grafton, West Virginia by Federal Troops On May 30, a force of Union troops, commanded by Col. Benjamin F. Kelley, were ordered and occupied the city of Grafton. They were ordered there to protect the Baltimore & Ohio Railroad, Washington's leading link to the western states and territories.
July 3, 1861 - Occupation of Martinsburg, West Virginia by Federal Troops On July 3, a Union force, commanded by Brig. Gen. Robert Patterson, arrived at Martinsburg. The Confederate force, commanded by Brig. Gen. Joseph E. Johnston, realized that they were outnumbered and quickly left the town, leaving Patterson to occupy it.
July 12, 1861 - Occupation of Beverly, West Virginia by Federal Troops On July 3, a Union force, commanded by Brig. Gen. Robert Patterson, arrived at Martinsburg. The Confederate force, commanded by Brig. Gen. Joseph E. Johnston, realized that they were outnumbered and quickly left the town, leaving Patterson to occupy it.
September 6, 1861 - Occupation of Paducah, Kentucky by Federal Troops In the morning of September 6th, a small squadron of 2 wooden Union gunboats and a few transports landed Union troops at Paducah, Kentucky, forestalling an obviously planned Confederate move from Columbus to the strategic Kentucky city at the mouth of the Tennessee River. There were not any casualties or any fighting. It was Brig. Gen Ulysses S. Grant's first major victory and it was a bloodless one. By seizing Paducah, and later, nearby Smithland at the mouth of the Cumberland River, Grant had prevented Confederate forces from claiming the entire state of Kentucky and planting their northern line on the Ohio River. The move also foreshadowed the river campaign of the coming year. Brig. Gen. C.F. Smith was assigned to command in western Kentucky as Grant returned to Cairo.
September 16, 1861 - Occupation of Ship Island, Mississippi by Federal Troops On September 16, the Confederate forces evacuate Ship Island, leaving it wide open for the nearby Union naval flotilla. After all of the Confederates were gone, the USS Massachusetts landed on the island, with its crew taking possession of the island. A Union prison would eventually be established on Ship Island.
September 22, 1861 - Occupation of Osceola, Missouri by Federal Troops On September 22, James H. Lane and his Kansas Brigade entered the town of Osceola. The townspeople were pro-Southern and when Lane discovered that there were military supplies and munitions in the local warehouses, this gave him a reason to destroy the town. Lane gathered up some wagons and loaded up as much supplies as he could carry. Nine citizens were court-martialed and shot, and then all but 3 buildings were set on fire, including the courthouse. Lane's force left town with 350 horses and mules and 200 slaves. The town ceased to exist with $1,000,000 worth of property stolen or destroyed.
September 26, 1861 - Occupation of Salt Works Mine in Clay County, Kentucky by Confederate Troops On September 26, a Confederate force, commanded by Brig. Gen. Felix K. Zollicoffer, entered Clay County. They managed to capture the Salt Works, being abandoned by the local Federals.
November 5, 1861 - Occupation of Prestonburg, Kentucky by Union Troops On November 5, a Union force, commanded by Brig. Gen. William Nelson, entered the town of Prestonburg. Confederate forces had evacuated the town earlier. Nelson's force officially occupied Prestonburg.
November 9, 1861 - Occupation of Beaufort, South Carolina by Union Troops On November 9, the Union expeditionary force, commanded by Brig. Gen. Thomas W. Sherman, landed at Beaufort. They quickly occupied the town.
November 24, 1861 - Occupation of Tybee Island, Georgia by Union Troops On November 24, a Union force arrived at Tybee Island. On the nearby Savannah River, the troops were helped by the USS August, USS Flo, USS Pocahontas, USS Savannah, and the USS Seneca. Soon, the land troops were able to occupy the island.
December 3, 1861 - Occupation of Ship Island, Mississippi by Union Troops On December 3, a Union force, commanded by Maj. Gen. Benjamin F. Butler, was joined by the steamship, USS Constitution, at Ship Island. Together, they landed on the island and occupied it. This lasted for the duration of the war.