St. Marys is a city in Auglaize County, Ohio, United States.

Founded in 1823, the city is located on a portage between the St. Marys and Auglaize river systems, which was a significant factor in its development before the era of canals.

Girty maintained his trading post between 1783 and 1790 and fled when General Harmar's army approached.

[citation needed] When General Wayne returned through the St. Marys area late in 1794 after the Battle of Fallen Timbers, he found the site deserted but noted its strategic location as a portage between the St. Mary's River and Auglaize River.

Fort St. Mary's, named for the nearby river, was built by a detachment under Lieutenant John Michael in Oct. 1795 following the Treaty of Greenville.

St. Marys was founded by William Houston and John McCorkle, and Charles Murray, in 1823.

They bought 400 acres (160 ha) of land and laid out the village of 68 lots.

The village was incorporated as a town in 1834 and Judge Stacy Taylor was elected its first mayor.

[8] Three properties in St. Marys are listed on the National Register of Historic Places: the former Fountain Hotel,[9] the Dr. Issac Elmer Williams House and Office,[9] and the former Holy Rosary Catholic Church, which was destroyed one year before it was placed on the Register.

[9][10] St. Marys is a part of the Tree City USA national program.

28.9% of all households were made up of individuals, and 12.6% had someone living alone who was 65 years of age or older.