The twenty states that supported the Union were the following (with their capitals)
1. California – Sacramento 
2. Colorado – Denver 
3. Connecticut – Hartford 
4. Delaware – Dover 
5. Iowa – Des Moines 
6. Illinois – Springfield 
7. Indiana – Indianapolis 
8. Kansas – Topeka 
9. Maine – Augusta 
10. Massachusetts – Boston 
11. Michigan – Lansing 
12. Minnesota – St. Paul 
13. New Hampshire – Concord 
14. New Jersey – Trenton 
15. New York – Albany 
16. Ohio – Columbus 
17. Oregon – Salem 
18. Pennsylvania – Harrisburg 
19. Rhode Island – Providence 
20. Wisconsin – Madison
These twenty states chose to remain loyal to the Union during the American Civil War by providing troops, military supplies, financial resources, and generally upholding the Federal government’s authority against the Confederate states. President Abraham Lincoln famously declared that the War was “maintained, on the part of the Union, for the cause of maintaining the nation’s full integrity”. In other words, these states were loyal to the Union, despite the pressure from the Confederacy to secede. The loyalty of these states was critical in winning the Civil War and preserving the Union.