I have been very unsuccessful in locating a homeowner of an abandoned property. I have used the people search sites online and none are accurate. Can anyone offer some suggestions on how I can track down this homeowner? Thanks 

Pulling tax information via your state's online search tool?

Those tax bills have to be mailed somewhere.  You can also try stopping by the property and talking to the neighbors.  Lots of times a neighbor may help keep the outside of the property in pretty good shape for the homeowner.  They'd likely have the info needed to contact the owner.

Property tax records are as accurate as the abandoned property owners are reliable for their tax payments. Not so much. The best advice that @Steve M.  gave was talk to the neighbors. Another less ethical practice is, place a for sale sign out front with your number on it. The owner will call if they are around, and they will be angry. So be prepared with your reasoning for placing the sign. And be understanding that you are in the wrong if you do place a sign. Don't argue, basically apologize; and explain that you had exhausted all other means of locating them, to see f they were interested in selling the property.

I agree. Start with neighbors and compare anecdotal evidence.

Search social media

Pay for skip tracing services.

Hire a PI at $75+/hour if the deal is juicy.

One time I couldn't locate an owner.  His last name was uncommon, so I wrote a letter to everybody in the country with that last name, inquiring about so and so.  I didn't reach the owner but did reach a relative who passed my contact info to the owner.  successful outcome.

If in a small town, the post office employees may know where the person moved to even after the forwarding has expired.  I had an address for an owner in CA and called the post office and asked for the postmaster.  Told the PM that I was looking for Mrs. X who used to live at xxx Street.  He knew her and she moved to a neighboring town and I was able to contact her.  Another success.  

Great suggestions, thanks everyone for your input.