More from Mike C:
There may be another way to view this "unexpected acquisition" question. This morning it occurred to me that I've been looking at it from the perspective of the city of Philadelphia acquiring parcels of land for Cobb's Creek Park, which they did by some form of eminent domain, paying the owners for a number of large properties, some of which included the estates of the Ashhurst's, the Elliott's, the Equitable Trust Company, the Wolfenden's, and as mentioned, land owned by the PA Railroad Co, which intersected the land of today's Cobb's Creek course. All of those transactions took place in the 1910-11 timeframe, however, and then became part of the larger parcel known as Cobbs Creek Park.
Early reports about the agreement of the city to use land within the park for a golf course talked about 91 acres in the northwest boundary of the park. Much like Merion, during the acquisition/design phase it was determined that more land was needed for the type of course they wanted, and eventually the course that was designed and built ended up being roughly 125 acres, again much like Merion. It could be that there had to be some convincing on the part of the GAP design committee negotiating with the city to get more land for the course, which could have been just a logical extension further to the southeast by 35 acres or so from what the city originally agreed to.