William and Anna's ca1894 marriage record would have been recorded at the Register of Wills office in whichever county they got the license. It might have info on his parents and birth place. You should be able to get his death certificate directly from the PA Div. of Vital Records. Hopefully it has his parents names and possibly where he was born. His obituary might also have this info. Check with the Northeastern Pennsylvania Genealogical Society in Shaverton to see if they can help you find it.
The 1900 census shows they were married 6 years and he immigrated in 1889 and was a naturalized citizen. His naturalization papers are probably at the Luzerne County Prothonotary Office. The papers might have exactly where he was born, when he came over and on what ship.