Slavery in Maryland lasted over 200 years, from its beginnings in 1642 when the first Africans were brought as slaves to St. Mary's City, to its end after the Civil War. While Maryland developed similarly to neighboring Virginia, slavery declined here as an institution earlier, and it had the largest free black population by 1860 of any state. The early settlements and population centers of the province tended to cluster around the rivers and other waterways that empty into the Chesapeake Bay. Maryland planters cultivated tobacco as the chief commodity crop, as the market was strong in Europe. Tobacco was labor-intensive in both cultivation and processing, and planters struggled to manage workers as tobacco prices declined in the late 17th century, even as farms became larger and more efficient. At first, indentured servants from England supplied much of the necessary labor but, as their economy improved at home, fewer made passage to the colonies. Maryland colonists turned to importing indentured and enslaved Africans to satisfy the labor demand. By the 18th century, Maryland had developed into a plantation colony and slave society, requiring extensive numbers of field hands for the labor-intensive commodity crop of tobacco. In 1700, the province had a population of about 25,000, and by 1750 that number had grown more than five times to 130,000. By 1755, about 40% of Maryland's population was black, with African Americans concentrated in the Tidewater counties where tobacco was grown. Planters relied on the extensive system of rivers to transport their produce from inland plantations to the Atlantic coast for export. Baltimore was the second-most important port in the eighteenth-century South, after Charleston, South Carolina. In the first two decades after the Revolutionary War, a number of slaveholders freed their slaves. In addition, numerous free families of color had started during the colonial era with mixed-race children born free as a result of unions between white women and African-descended men. Although the colonial and state legislatures passed restrictions against manumissions and free people of color, by the time of the Civil War, slightly more than 49% of the black people (including people of color) in Maryland were free and the total of slaves had steadily declined since 1810. During the American Civil War, fought over the issue of slavery, Maryland remained in the Union, though a minority of its citizens – and virtually all of its slaveholders – were sympathetic toward