Cindy â€” you can take a simple approach and measure with tape measures and the like, but there are colleague lawyer friends of mine who make their entire incomes from property line disputes involving, fences, trees and encroachments.
It seems that everyone is getting along and it's okay. But there's a lot of potential risk and issues that may stem from a boundary that is unclear especially when the property changes hands.
The first step I'd suggest is to look at your escrow and title documents to see what's stated there in the legal description. If things between you and your neighbor are good, ask them to do the same with their documents and you can jointly compare notes. If your papers disagree with each other then you may want to look at the City and County Records to see what the property line is. Ultimately you may want to retain a land surveyor to really delineate. Important to note that if there is a defect or conflict it may implicate some error that could and should be remedied that may implicate mortgage and/or title insurance issues. This all matters because you guys might not always be neighbors or friendly neighbors. Better to have certainty.
Let me know if you need references to good property attorneys.