Massachusetts militia passing through Baltimore, 1861 (1862-1867).

Massachusetts militia passing through Baltimore, 1861 (1862-1867). Baltimore is the capital of the state of Maryland. Although a slave state, Maryland did not secede from the Union before the outbreak of the Civil War. However, when Union troops marched through the city in April 1861, pro-Confederate sentiment led to rioting. After the disturbances, which resulted in the death of 12 civilians and 4 soldiers, federal troops occupied the city to ensure that Maryland did not secede and leave Washington DC encircled by Confederate territory. An engraving from volume I of The War with the South : a History of the Late Rebellion, by Robert Tomes, Benjamin G Smith, New York, Virtue & Yorston, 3 Volumes, 1862-1867. (Photo by The Print Collector/Print Collector/Getty Images)