The Library of Congress American Memory Project has a few maps you might find useful.
Bacon's steel plate map of America, political, historical & military(1863): "Federal free states" are outlined in red, "Federal slave states" are yellow, "Federal territories (free)" are orange, and "Confederate states (slave)" are green.)
Colton's map of the southern states … (1862): Map is colored to show "free, or non-slaveholding states" (pink), "border slave states" (yellow)…)
Slavery and Emancipation in the United States, 1777-1865 (Ancestry.com) National map of the United States showing the progress of slavery and the abolitionist cause, 1777-1865.
Slavery in the American South: 1790-1860 (interactive from University of Oregon)
Compromise of 1850: Status of Slavery (interactive)
Kansas-Nebraska Act: 1854 (interactive)
