How has this not been added until now when it took place in 1993?
I know this area VERY well and live about 20 minutes from where the body was left...and can give you some information on the area that hopefully will be of use to someone around here.
For those not from Pennsylvania or surrounding states with toll turnpikes, the PA Turnpike has several service plazas. These have been a part of the Turnpike since it opened in 1940 and typically have a gas station, restrooms, several restaurants, and restrooms. Like rest areas on other interstate highways, they are typically only accessible from one side of the Turnpike.
Butler Valley Service Plaza, which sat at mile marker 31, was demolished in 2002 as part of a project that built a new toll plaza at that location. The idea was to better connect I-79 (a freeway) and I-76 (the Turnpike); it also eliminated the old Cranberry toll plaza. (Cranberry is the nearest exit, at mile marker 28, and is also where I-76 links up to I-79; in 1993, this would have required exiting the Turnpike and getting on US 19).
The Butler Valley plaza was only accessible when traveling westbound. (Its companion plaza, the Zelienople Service Plaza, was eastbound only, located about ten miles east of this one, and operated for six more years after Butler Valley closed).
As inferred in the previous paragraph, the site of the service plaza where this incident occurred is now a large toll plaza, which only works with the EZPass or Toll by Plate today (the PA Turnpike stopped taking cash altogether last year).
Since this is only accessible from one side of the highway, there are a few theories in play here:
1. The perpetrator who left the baby there was from the area, likely from one of the suburbs east of Cranberry which is served by the Turnpike.
2. The perpetrator was from the other side of the state, though anyone who knows anything about PA's toll rates, even in 1993, would be able to quickly say this is far less likely.
3. A long shot, but someone could have come up from I-70 in an area further south, as it does become the Turnpike further east of here.
4. Also a long shot, but it could have been someone who was from west of the area, had the baby somewhere in PA, and decided to dump the baby in PA before crossing into Ohio (which also has a system of service plaza) or any other point west. (The PA and Ohio turnpikes connect 31 miles west of this service plaza; the Ohio Turnpike then splits off 23 miles into the state, with I-76 continuing as a freeway and the Turnpike becoming I-80).
Locals do use the Turnpike, in spite of its tolls, to get from the Hampton/Richland/Shaler areas (exit 39) and Indiana/Cheswick/Springdale*/Tarentum/Fox Chapel areas (exit 48) to Cranberry. Exit 57 is Monroeville/Murrysville and was the most direct connection to Pittsburgh itself at the time (prior to the I-79 interchange being fully completed). The Turnpike can create anonymity among travelers, as this perpetrator may have blended in easily with, say, a Philly resident going to Cleveland.
* of note, Springdale is where Kathleen Kelly disappeared from in 1981
One final remark: keep in mind this happened in 1993. There were likely no cameras anywhere at these service plazas at the time (I don't recall there being any and took Turnpike trips to the Philly area that included service plaza stops in both 1992 and 1994). Most people just went in, got some food at Roy Rogers or McDonald's, maybe had a sit-down meal at Bob's Big Boy at some of the more eastern plazas (now THERE'S a name from the past!), and ignored most of the other travelers. Nobody really was searching for anything suspicious or on heightened alert in that day and age.
Sadly, these cases seemed to happen a lot back then. It's like the baby found in Gloucester County, NJ in 1986--someone dumped a newborn somewhere.