People not familiar with the geography typically pronounce the "LAN" part of Lancaster as if they were talking about a Local Area Network. There should be no additional stress on any of the syllables.
~ Blue Jays ~
I lived in that general area once and almost all outsiders mispronounce it. I was born and raised in New Madrid county Missouri and that's routinely mispronounced too.
New MAD rid, not New Ma DRID.