Clark W. Griswold, Jr. wrote:

You start with your city/county property office and obtain
a plat of the area you live in. Many municipalities have this
online now. That will give you a rough idea of the property
boundaries, including distances from landmarks and other features
that should give you an close approximation of the boundary.

Yes, when faced with this situation I was able to go to the
city and examine maps called sewer sheets. On these, the
distance from the sewer plug (near the sidwalk in our case)
to the where the property line intersects the street is marked.
So this will tell you where you property lines with your
next-door neighbors are, within a few inches, at the front
of your property. Also marked on this map is the angle
at which the property lines intersect the street (in my case,
81 degrees). From this you can extrapolate where the
property line heads as you go towards the back of the property.

However, if the properties are decades old the defacto boundary
as determined by usage may have more legal significance than
the surveyed boundary anyway.

Steve