Industrialization trolley lines and factories opened boosting the local and commuter population. Index of civil war Hypertext on Amer. Hostory-late History of American's ninteenth century.   Mill Town saw and then cotton mills were built along the creek.   Mill Creek Sewer The Mill Creek sewer was built not only for the purpose of disposing wastewater, but more importantly for the purpose of accommodating city growth. Removing the creek from the land's surface made that land more developable. Though it would have been more wise to run the Mill Creek sewer under streets, Planners wished to continue the existing grid network through the Mill Creek area. The Mill Creek is very large, however, and could not efficently or cost-effectively follow the grid pattern. This, the creek's sewer currently crosses several streets and runs under hundreds of homes in West Philadelphia.   1860's:lay sewer pipes 1880:construct the Mill Creek sewer   1854:Mill Creek becomes part of Philadelphia 1855:Fairmount Park created 1863-1878:1st modern contiguous development of Mill Creek 1872:open the zoo   Population 1830:14,473 Blacks in the city of Philadelphia and suburbs 1860:23,738 total population of Blockley-West Philadelphia...mostly of Irish, British and German descent 1990 Census Data Set