Puritan laws were strict, and adherents of other denominations, such as Quakers, were driven out of Medford. Collins was the first slave owner in the town, but others followed. Both American Indians and African Americans were enslaved within the Massachusetts Bay Colony, and, as in the South, slaves were commonly whipped for even small transgressions. Not until 1783 was slavery outlawed in Massachusetts.
The first bridge across the Mystic had been constructed in 1637 at the site of the present-day Cradock Bridge; this toll bridge remained the only crossing aside from fords and ferries until 1787, boosting Medford's economy as Boston and other New England cities grew. It also brought the Flying Stage-Coach line from Portsmouth, New Hampshire to Boston in 1761 and several more over the next two decades. Taverns were opened to serve travelers, the oldest being Daniel Woodward's (1690). Blanchard's Tavern, popular for sleighing and dancing parties, was the terminal of the Medford and Boston Stage Coach Line (2). As Medford grew, services were added. By 1785, the Medford Amicable Fire Society was formed, and three years later the first almshouse was opened on Canal Street. President John Adams appointed the first Medford postmaster, Samuel Buel, around 1800. During the American Revolution, Medford citizens resisted the British first by refusing to pay taxes or sell supplies to England, hiding stores of saltpeter, and forming a company of 59 Minutemen led by Isaac Hall. On April 18, 1775, Paul Revere rode over the Medford Bridge and warned Hall that the British were approaching on their way to Lexington and Concord. The Medford Company joined the Reading Company for the battle at Lexington, then Bunker Hill, Ticonderoga, Morristown, Stillwater, and Valley Forge. A second company formed to protect Medford itself. A field hospital was set up on the south end of the bridge, and entrenchments built on Winter Hill, where Winthrop's home had once stood. Refugees from Charlestown and Boston were sheltered in Medford. Sarah Fulton nursed soldiers at the field hospital and acted as courier between troops in Boston and Medford. Only two Medford citizens left to join the British: Colonel Isaac Royall and brick-maker Joseph Thompson.
With the opening of the Middlesex Canal at the beginning of the nineteenth century, Medford became an important ship-building town. Other industries with long histories in the town expanded, as well, namely brick-making and the distilling of rum. The 1830s brought the first railroad, the Boston and Lowell Railway. Medford officially became a city and elected its first mayor, Samuel Crocker Lawrence (a Civil War General for the Union), in 1892. Four years later, in 1896, the Medford Historical Society was formed.