The first time we see the construction crew in Pennsylvania, a train passes through in which the first two have CN in white letters on the side. CN stands for Canadian National, a railway that stretches through Canada and down to the Gulf of Mexico, but does not pass anywhere close to Pennsylvania. This may indicate that this scene was not filmed in Pennsylvania.
When examining the decomposed body of Mrs. Hughes, Walter observes that she had systemic lupus erythematosus (SLE), and goes on to state that she would have been "incapable of producing offspring." Such a statement is not true. Lupus is an autoimmune disease, and while it can cause complications with pregnancy, many women with lupus can, and do, successfully bare children.
There is no such thing as the Lansdale Sheriff Department. There is the Lansdale Borough Police Department, and the Montgomery County Sheriff Department. However, sheriff departments don't have much involvement in Pennsylvania. It is more likely that they would be dealing with the Pennsylvania State Police.
The newspaper article is dated 9/18/1992 regarding the investigation into the deaths of Evelyn Hughes and son. When their remains are being exhumed, the headstone lists Evelyn Hughes date of death as 11/4/91 and Baby Boy Hughes as 11/1/1991.