Navigation Company would become heavily involved in the improvements. The dam initially submerged the rapids, and later developments transformed the stretch of the Schuylkill between the dam and East Falls from a tidal river into a slack water river resembling a very long freshwater lake. The placid man-made surface was ideal for ice skating in winter and rowing in summer. In 1835, the first regatta took place between the Blue Devils and the Imps Barge clubs. The excitement from the race sparked the formation of several barge clubs, many of them short-lived. The frame boathouses A secondary effect of taming the Schuylkill was that the calm water provided a breeding ground for mosquitoes, which drove wealthy residents from their riverside mansions. The abandoned estates were bought by the City of Philadelphia. In 1844, the City purchased the Lemon Hill Estate. The leaseholder of Lemon Hill operated a beer garden and allowed rowing and barge clubs to build frame structure boathouses on the Estate's property along the Schuylkill. In 1855, the City founded Fairmount Park by converting the Lemon Hill Estate, upon which the frame boathouses were built, into a public park. At the same time, some of the established clubs wanted to regulate the sport of rowing to prevent unscrupulous practices and fixed races. As a result, in 1858, the Schuylkill Navy was founded, which eventually transformed the professional sport of rowing into an amateur sport. In 1859, the City condemned the boathouses along the Schuylkill. Boathouses of 1860 Although the City condemned the frame boathouses, it passed an ordinance in 1860 to permit construction of three new boathouses for Pacific Barge Club, the clubs of the Schuylkill Navy, and the Philadelphia Skating Club. After 1860, without city approval, several clubs constructed one-story boathouses similar to the frame structures that the City had previously condemned and removed, but these newer boathouses were built with brick and stone. In 1868, following an expansion of Fairmount Park, the City ordered the removal of all of the one-story brick and stone boathouses except for buildings belonging to the Philadelphia Skating Club (#14 Boathouse Row), Pacific Barge Club (#2-3 Boathouse Row), and Bachelors Barge Club (#6). Post–Civil War boathouses Between 1869 and 1871, Pennsylvania Barge Club and Crescent Boat Club erected a double boathouse at #4 and #5 Boathouse Row. In 1871, the Fairmount Park commission allowed the University Barge Club and the Philadelphia