The county was named for Cecil Calvert, 2nd Baron Baltimore (1605–1675), the first Proprietary Governor of the Province (colony) of Maryland.It is the only Maryland county that is part of the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD Metropolitan Statistical Area The area now known as Cecil County was an important trading center long before the county's official organization in 1674 by proclamation of Lord Baltimore.Engineer James Rumsey, who grew up in Bohemia Manor before moving to Bath, Virginia (or Berkeley Springs, West Virginia), invented a steamboat which he demonstrated to George Washington, before traveling to London to secure patents against competition from John Finch.Rumsey died there in 1792, but his lawyer brother Benjamin Rumsey moved south to Joppa, Maryland and served as Maryland's Chief Justice for 25 years.Another early developer was George Talbot, appointed Surveyor-General of Maryland in 1683, Until the American Revolution, Cecil County was an important shipping center, both within the colonies and abroad.It exported not only its own agricultural products but also animal skins from the west and tobacco from the south. Francis Xavier Church (Warwick, Maryland) begun as a Jesuit mission in 1704 and rebuilt in 1792, is one of Maryland's oldest churches, though now a museum. Mary Anne's Episcopal Church, authorized in 1706 and rebuilt in 1742 is another (and still in use, as well as maintaining a historic graveyard).West Nottingham Academy founded by Presbyterian Rev.Samuel Finley in 1744, educated Benjamin Rush and Richard Stockton, both of whom signed the Declaration of Independence, and still operates today (though disaffiliated from the Presbyterian church and with additional buildings).
However, between 18, with financial support from the states of Maryland, Delaware and Pennsylvania, over 2600 workers built the 14 miles long Chesapeake and Delaware Canal, which became for a while the busiest canal in the new nation. Railroads and bridges also proved economically important to Cecil County and surrounding region.
British troops also destroyed most of Havre de Grace in nearby Harford County, Maryland.
Cockburn's ships then traveled up the Sassafras River, and, meeting resistance, destroyed Georgetown, Maryland and Fredericktown, Maryland.
No Civil War battles occurred in Cecil County, but residents had strongly divided loyalties.
Slavery had declined from 3400 slaves in the county in 1790 to just 800 in 1850.