Avenida Leandro N. Alem is one of the principal thoroughfares in Buenos Aires, Argentina, and a commercial nerve center of the city's San Nicolás and Retiro districts. By way of a beautification effort, Viceroy Juan José de Vértiz y Salcedo had a two-lane street built along what was then the shores of the Río de La Plata. Marking the estern[clarification needed] end of the city, the throroughfare was landscaped with cottonwood trees (alamos, in Spanish), and was thus inaugurated in 1780 as the Paseo de la Alameda. The paseo became a popular weekend promenade, and its contiguous shores an unofficial riverfront park popular with bathers until an 1809 edict banned the practice for reasons of "moral terpitude."
The frontage remained flood-prone, and in 1846, Governor Juan Manuel de Rosas had a contention wall six blocks long built along the paseo. Inaugurated in March 1848 as the Paseo Encarnación Ezcurra (in honor of his wife), Rosas had it renamed the Paseo de Julio that October in honor of the Ninth of July, date of the Argentine Declaration of Independence (the road's southern half was renamed Paseo Colón, in honor of Christopher Columbus, in 1857). An English Argentine investor, Edward Taylor, opened a pier along the promenade in 1855, and the flood-control walls were extended northwards to Recoleta, and south to San Telmo, in subsequent works completed in 1865.
Immigration in Argentina afterwards made the Paseo a veritable bazaar, in which Italian trattorias, French bistrots, German beer halls, and Greek restaurants operated alongside brothels and seedy bars. The increasingly commercial desirabity of the street, however, prompted the city to mandate in 1875 that all buildings along it be designed with porticos, a regulation still in force and one which forced the paseo's more precarious establishments to close.