My wife works for the county surveyor. Every week there's somebody looking for ammunition to use in a neighbor dispute. About 2/3s of these disputes are along the lines of, "Well, I went on OnX and saw my property lines, so I cut down a bunch of mature oak trees for firewood. Now my neighbor is suing me for cutting down my own trees.... what do you mean I was a dozen yards over the property line and those were his trees?!?! But, but, but OnX said! Man, I don't want to replace a dozen 100-year-old oak trees! Where do you even buy them at??"
Go to the county surveyor's office and pull your dang survey record. If the county doesn't have a survey on file, hire a surveyor to survey your property line. The $3k or whatever you'll pay for a survey - which is a whole whack of money - is a drop in the bucket compared to a lawsuit or insurance claim because your cut-rate fence guy put your chain link through the neighbor's garden, which you will have to pay to remove, and then pay to replace.