I agree with those that say find the property lines. Find those stakes with a metal detector before you say anything to the neighbor and if you can't find the property line/stakes, you may have to hire a surveyor to come out and mark off the property. No need to make the neighbor mad before you're sure you are in the right. Those stakes are there somewhere but you have to find them and if you can't the surveyor can.
So there are seriously metal stakes in the ground on people's property lines? I never heard this...