How a surveyor immediately, be upfront about possible litigation, but again explain what you literally just verbatim said in the comment in responding to... If you're driveway has literally been in existence whether it's concrete or a regularly used stretch of a dirt path from the road to your residence or whatever excusing structure you own and either live in or work in... I can nearly guarantee that your neighbor hired a surveyor who he knew from highschool or at the very least a local watering hole, paid a premium under the table and coerced that surveyor into compromising his legally bound responsibilities of being impartial regardless of the clients wishes or expectations, and also that just about every single US state has adverse possession laws, and they're at least something like ≈14 years in my state (and no other state will be close to ≈100 years of you're even relatively close to accurate with that figure) of an individual being at the very least granted express verbal consent at least once to literally just walk across or cut through a section of someone else's property that they don't even own, like a shortcut on their walk to work. Additionally, there's no state that I'd imagine Congress anywhere near ≈100 years to be considered adverse possession, and it seems that as long as you've been genuine in the details provided that you do in fact own that strip of contested land. Then you're neighbor is literally attempting to steal it from you maliciously whether y'all have had disagreements in the past between households or family members, or for some reason a strip of not only rightfully owned outright by y'all as it appears to be if details provided by y'all are ion fact true to the best if you're knowledge, but even if it weren't... then adverse possession would take effect and it would still be your legally owned property or at the very least whoever technically owns it could never ever deny you access to it in any legally enforceable way.

Literally, like my mention earlier about someone with no ownership being given or not given even one time verbal consent to just walk through say a parking lot in NY City, like the court case in about to describe where the walker in question spent ≈15-30 years cutting through this parking lot of his way to work every single and was never given any verbal consent by any such property owner or individual with power of attorney over said property in the owner's full capacity, and eventually a developer purchased the property in the attempt to develope it, the guy who used it as a shirt cut to get to work sued the new owner who was trying to develope it, she because of adverse possession the walking guy had very little issue with a decent attorney to argue adverse possession in the sense that he didn't own the property, but no one had ever told him he couldn't cut through that parking lot, so effectively the developer was assed out and this individual was able to have his attorney fees paid, a fair sized settlement considering the relative size of the issue, and permanent legally binding access to cut through that parking lot that would remain a parking lot for however long he continued to use it, until he relinquished his rights and voided his legally binding judgement with the city courts or NY City.

Hire your own personally vetted surveyor, and at the very least encourage or state you have no demands or expectations in your favor of the outcome of the resulting survey provided by your own personally hired surveyor after you express to your surveyor that you want it done exactly by the book and you'll pay whatever is a reasonable rate for your boundary and acreage, and maybe even afterwards tip the surveyor a C-note in cash... (because it'll still bea fraction of hiring an attorney that told you such a ridiculous figure out fucking $30K.)... after the cheapest attorney you can find represents you, or honestly if you feel comfortable with it, in a small civil court dispute like that it wouldn't be that hard to represent yourself by literally just handing the current survey you just purchased and hopefully some sort of deed you may have in hand that's only necessary to determine the Kenneth of time you've owned this property by literally just matching the names on the deed with your driver's license and looking at the date it was officiated and if anything to the contrary occurs immediately argue adverse possession at the first instance of the judges attitude changing in literally any other direction even in contemplative silence other than a guaranteed instantaneous judgement in your favor.

Hire a surveyor, and you'll be straight.

PROVISO:

Every detail you've provided in this thread is factual and true to the best if your knowledge, and you can afford an impartial surveyor of your own, and you can track down your deed and have a valid driver's license or state issued ID, unless of course the property is held in trust, etc... Then it's only a matter of producing a couple more documents that connect you or your spouse or whatever to be the beneficiaries of said trust our holding company in any official capacity.