The St. Joseph's Convent (a.k.a. Motherhouse) and adjoining St. Joseph's Academy are located at 605 Stevens Avenue in Portland, Maine (Cumberland County), near the geographic center of the city and possess integrity of location, design, setting, materials, workmanship, feeling and association. The buildings are locally significant under National Register Criterion A in the areas of Education and Social History and under Criterion C in the area of Architecture. The period of significance runs from 1862, when the St. Joseph's Academy building was constructed, to 1966, the 50-year cutoff for National Register properties. The St. Joseph's Academy served as a Catholic school for girls from 1882 until 1969, while the Motherhouse was the principal residence for the Sisters of Mercy stationed in the Diocese of Portland from 1909 to 2004. The site was an important educational, residential, and spiritual center for the Sisters of Mercy for over 120 years. Further, the buildings are architecturally significance as well-preserved examples of the Second Empire and Classical Revival styles. In addition, the Motherhouse represents the work of Boston architects Chickering & O'Connell, one of New England's preeminent ecclesiastic design firms during the short duration of its existence from 1901 until 1911. As a result of its religious associations, the property meets Criterion Consideration A for National Register listing. The property's significance is due to its historical associations with the local community and for its architectural significance rather than for any religious associations