Dix and Wool (updated)

On this date in 1861, the day before his 63rd birthday, Major General John Dix (above) was appointed to command the Department of Maryland. In that capacity, he would make judicious use of Lincoln's suspension of habeas corpus to arrest a few key Confederate sympathizers, including members of the state legislature, to such effect that secession was avoided. These tactics have been much decried, including by US Chief Justice Roger Taney (author of the Dred Scott decision), from that day to this. But, if the arrests did serve to prevent secession, they were undoubtedly a military necessity. With Virginia already the strongest part of the Confederacy, Washington, DC could not have survived in Union hands if surrounded by another rebel state.

In 1863, Dix took over the Department of the East from the considerably older Major General John Wool (below), whose distinguished Civil War service included the capture of Norfolk, Va. 

The move was made during -- or in the immediate aftermath of -- the New York City draft riots, which Wool had worked hard to suppress despite a shortage of troops on hand. The old soldier returned to his home town of Troy, NY, and despite his repeated requests never received another command. Wool is buried in north Troy, in the same cemetery as the Rock of Chickamauga.

(July 24 update:) Some say the threat of secession was exaggerated in Maryland in 1861. But in another crucial border state, Kentucky, it persisted well after that, as I was surprised to discover in researching my Granger book. The Union major generals overseeing civil affairs in Kentucky at the end of 1862, Horatio Wright and Gordon Granger, were seriously concerned about the possibility of that state seceding, and took steps to forestall it.