In 1849,on a mission to establish a presence for the Society of Mary in America, the Rev. Leo Meyer, S.M., journeyed from Alsace in France to Cincinnati. But with a cholera epidemic raging to the north, Bishop John Baptist Purcell of the Cincinnati diocese, sent Father Meyer to Emmanuel parish in Dayton to tend to the sick. In Dayton, Father Meyer met local farmer John Stuart, who had lost his infant daughter Mary Louisa to cholera the year before. Heartbroken, Stuart and his wife wanted to sell their Dewberry Farm property and return to Europe.
On March 19, 1850, Father Meyer, joined by three Marianist brothers — teacher Maximin Zehler, cook Charles Schultz and gardener Andrew Edel — purchased the 125-acre hilltop farm from Stuart and renamed it Nazareth. Stuart accepted a St. Joseph medal and a promise of $12,000 at 6 percent interest. The property included vineyards, an orchard, a mansion, various farm buildings, and the grave of Stuart's daughter, which Meyer promised to maintain.
Just a few months later, the University of Dayton had its beginnings on July 1, 1850, when St. Mary's School for Boys opened its doors to 14 primary students from Dayton. In September, the first boarding students arrived and classes moved to the mansion. Five years later, the school burned to the ground, but classes resumed within months. By 1860, when Brother Zehler became president, the enrollment was nearly 100 students. The Civil War had a little direct effect on the school because most of the students were too young to serve. College preparatory classes started in 1861 along with a novitiate and school for Marianist candidates. The school would become Chaminade High School, named after the order's founder William Joseph Chaminade, which has since merged with the all-girls Julienne High school run by the Sisters of Notre Dame de Namur to form the co-educational Chaminade-Julienne High School.
The core of the Historic Campus was built during this time, starting in 1865 with Zehler Hall, the iconic Immaculate Conception Chapel in 1869, and St. Mary's Hall, then the tallest building in Dayton in 1870.[12] In 1882 the university was incorporated and empowered to confer collegiate degrees by the State of Ohio.