This town was built on the north bank of the St. Marys River at a place called Buttermilk Bluff. The original tract of land, containing 1620 acres, was purchased by the proprietors for laying out the Town of St. Marys for Jacob Weed for thirty eight dollars each on Dec. 12, 1787. The city was first laid out by James Finley, County Surveyor, in August 1788 and recorded Jan. 5, 1789. The twenty proprietors were: Isaac Wheeler, William Norris, Nathaniel Ashley, Lodowick Ashley, James Seagrove, James Finley, John Alexander, Langley Bryant, Jonathan Bartlett, Stephen Conyers, William Ready, Prentis Gallup, Simeon Dillingham, and Richard Cole.
The city was laid out a second time as authorized by Act of Dec. 5, 1792. Map of town drawn by Parker, Hopkins, and Meers, certified by James Parker, County Surveyor, Jan. 3, 1792. The town of St. Marys was incorporated by an Act passed Nov. 26, 1802.
St. Marys was the temporary county seat until the first courthouse and Gaol (jail) was erected at Jefferson (Jeffersonton) as authorized and named in Act passed Nov. 29, 1800. Jeffersonton was the permanent county for sixty-nine years (1801- 1871).
An election held Jan. 3, 1871 authorized by an Act passed on Oct. 27, 1870 for removal of county seat from Jeffersonton to St. Marys. St. Marys was the first permanent county seat for fifty-two years (1871- 1923). An Act of Aug. 11, 1923 authorized the removal of the county seat from St. Marys to Woodbine.