At the dawn of the Civil War, Nebraska was still a territory, with heavier populations in the east. Elibigle men living in the territory responded to the call for troops. This resulted unprotected western settlements in the territory. If we could travel back in time, we would see the southeast portion of the territory, primarily Nebraska City, providing a safe haven for people fleeing the fighting along the Missouri-Kansas border.
Nebraska provided about 3,300 soldiers to the Union Army. Of these 239 died in war, most from disease and not in battle. Shortly after the Civil War broke out, territorial Governor Alvin Saunders called for the formation of the First Nebraska Volunteer Infantry regiment. Troops boarded steamboats at Omaha in July of that year and left for Missouri. Some of these men were involved in major battles, such as Shiloh.
In 1863 the First Nebraska Volunteer Infantry was reconstituted as a cavalry regiment. They were furloughed to Omaha and assigned as the First Nebraska Cavalry to Fort Kearny in 1864. The second cavalry regiment was recruited for nine months to respond to the Santee uprising in Minnesota and the Battle at White Stone Hill north of Fort Pierre in Dakota Territory.
One of the largest repositories for military records in Nebraska is in Lincoln at the Nebraska State Historical Society. While they are currently closed for remodeling, it is definitely a place you need to visit when they reopen. They are located at 1500 R Street in Lincoln. A synopsis of their Civil War collection is:
Grand Army of the Republic (GAR Membership Rosters
Grand Army of the Republic (GAR) Burial Cards
Rosters of Nebraska Soldiers in the Civil War, 1861-1865 as published in Andreas's 1882 History of Nebraska
Rosters of Soldiers, Sailors and Marines, 1887-1925 (living in Nebraska during that time period)
Gerald E. Sherard has two large databases online for Nebraska Civil War soldier information. They are Nebraska Civil War Grand Army of the Republic Members Index and Nebraska Civil War Veterans' Data. In addition the Nebraska State Historical Society has a search form for their Nebraska Civil War Veterans' Database.
Other Internet web pages with good information include the Civil War Rosters - Nebraska Links and 1893 Roster of Nebraska Veterans-Nebraska Enlistees. The Nebraska Civil War Regimental Histories contains a good deal of interesting information.
A membership in Footnote.com gains you information from the compiled service records for Union Soldiers, Nebraska. It is about 95% complete. These are not pension records. If you do not have a membership in Footnote.com, you can access this at a Family History Center (LDS) near you.