Since you're from the states I would recommend starting off with the Oxford History of the United States series. I've read five so far;
1) The Glorious Cause: The American Revolution 1763 - 1789 by Robert Middlekauff
2) Empire of Liberty: 1789 - 1815 by Gordon S. Wood
3) What Hath God Wraught: 1815 - 1860 by Daniel Walker Howe
4) Battle Cry of Freedom: The Civil War Ear by James McPherson
5) Freedom From Fear: The American people in Depression and War 1929 - 1945 by David M. Kennedy
These are all great books and will not put a hole in your pocket. I would also highly recommend The Impending Crisis: America Before the Civil War 1848 - 1861 by David M. Potter. It's a bit dated but this book is considered the best book that covers the politics of the era. Good luck and happy journey.