When was the unions first victory?

Answer 1

It is important to note that there were many battles and skirmishes in the American Civil War and it is important for the both the historian and the informed student to focus on those military actions which have long range implications. George McClellan led a successful campaign in what is now West Virginia in the summer of 1861 as the Union was reeling from it's great defeat at the first

Manassas,

but the scale of the West Virginia campaign was small and its effects transient. The first important victory for the Union, in the view of many historians, was the capture of Fort Donnelson and Fort Henry in northern Tennessee in February of 1862, which signaled the successful beginnings of the largely successful Western Campaign and the ascendancy of Ulysses S Grant.