Hopefully this won't be seen as some variation of a poll. It just seems that most casual U.S. history buffs have very limited knowledge of events in the early 1860s that weren't related to the war, and I'm curious about other happenings during this time that fascinate experts on the period.
Im not a historian, but I have done a large amount of research in primary sources surrounding the US interaction with Europe and Russia during the Crimean War (1853-1856) which I feel is often overlooked in US history, partially because it is over shadowed by the US Civil War. Some aspects of the US relationship with Russia during the Crimean War are brought up in the context of the lead up to the Civil War. (The one that come directly to mind is the Ostend Manifesto, which was a plan proposed by Southern politicians to seize Cuba and turn it into a slave state. It hinged on Britain being too distracted by Russia during the Crimean War to help defend Spain's control over Cuba.) The gist of what I research was that the US came remarkably close to helping Russia during the war, which is almost never mentioned.
For example, when US diplomats traveled through Russia, the Russians often asked them where the US Navy was, because the assumed it was going to sail to Europe to support them. (Obviously that was never actually going to happen, but it displays the atmosphere that existed at the time.)
My main source was the journal of Daniel Coit Gilman who was a diplomatic attache in Russia at the time.