Besides housing Masses said in Italian, it sponsored a variety of social, humanitarian, and civic programs aimed at acclimating Italian immigrants to life in America. Immigrants from Italy began arriving in Baltimore in the early 19th century, and continued in a small but steady flow through the 1850s. They settled around President Street near the area today known as Little Italy. After the Civil War, immigration from Italy burgeoned. While some new arrivals were coming from all parts of Italy, most were artisans and laborers from Naples, Abruzzi and Sicily. They continued to settle along President Street, Albemarle, Stiles and Exeter Streets. By 1870, between one-third and one-half of that area's population was Italian and it eventually earned its name Little Italy. These devout Catholics sought out the nearest Catholic church, at that time St. Vincent de Paul on North Front Street. Beginning in 1874, St. Vincent de Paul sponsored Italian Masses, yet it was not adequate to handle such a large influx of non-English-speaking congregants, nor was it conveniently located for the Italian community. Therefore, the Archdiocese of Baltimore decided to establish an all Italian parish, as it had earlier for Irish and German immigrants. Part of the role of these ethnic churches was to acclimate immigrants to American life and assist in their assimilation. The lots for St. Leo's were purchased in June 1880 and construction began shortly thereafter. By the time the cornerstone was laid in September, the ground floor of the building was complete to a height of 10 feet. Parishioners begged the pastor to hold Mass even before the building had been completed - which he did. The building was dedicated one year later in September 1881. As the social and spiritual focus of Baltimore's Italian community (to this day), St. Leo's was the natural center for a variety of mutual aid societies, citizenship classes, and social service and community action organizations. Thus, for most Italian immigrants coming into Baltimore, it was the major institutional entry into American cultural, social, political and economic life. Architecturally, the church building represents an unusual mix of Italianate, Romanesque and Classical elements, and is a good example of High Victorian eclecticism applied to a church. Designed by E. Francis Baldwin, it represents the work of a major figure in late 19th century Baltimore architecture. It also presents an interesting contrast with the bulk of Baldwin's better-known work, which was in commercial and industrial architecture.