While I don't know where this particular railroad map came from, or even what time period it represents, just from the contents of it, the map must be an early one. It shows New Orleans and the place where the steamers used to depart from the southshore ( Milneburg), the steamer routes across Lake Pontchartrain, and then the stops made by the boats along the northshore (Mandeville and Lewisburg). Then the boats would head up the Tchefuncte River, stopping at Madisonville, and then continue on, taking the Bogue Falaya River to the Covington steam boat landing.
On the railroad side, the short line railroad from Mandeville to Abita Springs is not shown so it may not have been built yet. Instead, the railroad track comes out of New Orleans (Queen & Crescent Railroad), passes across the Rigolets, where it becomes the North Eastern Railroad, past Gusman to Slidell, then to Pearl River. There it takes the Poitevent Favre East Louisiana Railroad line across St. Tammany Parish westward through Florenville and Generelly and winds up in Abita Springs and Covington.
I found Florenville on an old road map, but Generelly was not labeled. It was probably in the same general area as St. Tammany Corner on older maps, known today as the St. Tammany community on La. Hwy. 36 near where La. Hwy. 434 runs into it. Click on the map below for a larger view.