If you are interested in Mennonite genealogy you could check out a book published in 2004 on the Mennonites in Franklin Co. PA and Washington Co. MD.  It is some 900 pages long. You can buy it from the LCMHS:   Building on the Gospel Foundation... 1730-1970 by Edsel Burdge Jr. and Samuel L. Horst.    It is not without a few errors in tracing some of the early Mennonite families back to Lancaster Co. in the very early years.    There has also been another huge Mennonite book published in the past few years.  It is over 1,000 pages long, and takes a county by county approach, in PA, OH, and elsewhere.  Can anyone help me recall the title?  I should recheck it myself as I've done so much more research after I first obtained it by interlibrary loan that I'd probably do well to recheck in it.    Much of the confusion/errors in pre 1850 genealogical research comes from many people with the same names living in the same counties.  For example, I have been researching a Christian Hershey who married a Mary Good.  At the same time a couple of other Christian Hersheys were living there in the late 1700's and early 1800s.  I found a couple of wills in York Co. with mention of the Christian Hershey name.  One John Hershey left in his will to both his son Christian Hershey and his son-in-law Christian Hershey.  John Hershey appears in a census record next to a Christian Hershey, but this could have been either his son, son-in-law, or the one I've been researching who left York Co. Mary Good  Hershey is said to have died in York Co., but there is no tombstone for her, and the Christian Hershey who left York Co. continues on with a wife in the same age range as Mary Good  Hershey.   Genealogy is like a box of chocolates:  if you pick them up wihout paying attention to where they were originally you can get them all mixed up, whether they are  Hersheys or not!   RB