Maryland

 
Historical Timeline
 1664  The first colonial "anti-amalgamation" law is enacted (amalgamation referred to "race-mixing".  Other colonies, including Virginia, soon followed Maryland's example.
 1750 61% of all British North America's 145,000 slaves live and work in Maryland and Virginia's tobacco fields.  
 1790 By this time, slavery is entrenched in the original 6 slave states: Maryland, Delaware, Virginia, North Carolina, Sough Carolina, and Georgia.

Slave Populations:

 

bullet1830: 107,499
bullet1860: 90,374

 

Washington D.C.

The nation's capital served as a center for the domestic trading of slaves; many lawmakers were slaveholders.  Slavery was not abolished in Washington D.C. until 1862.