R.f.d. With "Local" For Address In 1938

I need your help. I am trying to find information of what the markings on this cover means,

Jammyster, if you want to know what "local" is, it just means he lives in the same town as where the letter was mailed. In this case Mr. Martin appears to live in Sistersville, West Virginia!
RFD stands for Rural Free Delivery.

Peter

Of course, "RFD" is Rural Free Delivery.

Presumably Mr. Martin lived in Sisterville, WV, the namesake of the city/town where the cover originated. Many covers of this vintage, especially in smaller locations, often used the words "Local" or "City" rather than spelling out the entire city/state names.

Why do they call it "free" when the one mailing it used postage?

Jammyster, before the Rural Free Delivery system one would have to pick up ones mail at the post office, or pay someone to deliver it to you if you lived "in the boondocks". The letter above, from Sistersville, was most likely addressed to someone that lived several miles away from town, hence the "RFD" indication.
Personally, I live in the unincorporated part of the county, and I live on Rural Route #3. Up until some twenty years ago some of my mail was still addressed with "RFD".

Peter

Mailed at the 2 cent rate for a local letter mailed at an office with carrier service. This rate ended in 1944. Had Mr Martin lived outside of the Sistersville territory, the letter would have cost 3 cents.

As an aside, here are 4 ways of addressing a local letter, all sent within Wilmington, Ohio. The "Wilmington" method is sure more foolproof than just saying city, local or town.

I can't add anything to all the excellent explanations you have been given other than to mention that there was a television show in the late 1960s and early 1970s
called "Mayberry R.F.D." It was a spinoff of the well known "Andy Griffith Show" that starred Andy Griffith, Don Knotts, and Ron Howard. The spinoff was trying to keep the series going with just the supporting cast after Andy Griffith left the show. It only ran for about 3 or 4 seasons as I recall. The R.F.D. in the show name was of course referring to the fact that the ficticous town of Mayberry was very rural and so mail was delivered to most of the tiny population using Rural Free Delivery.

An historical marker providing some information on Sistersville, WV:

Thanks. It came from my father's stamp collection. It was addressed to his father that lived on a farm a little ways from the main street downtown. I am putting some shadowboxes together of my father's stamps and sometime related to the family for Christmas. Thanks for your help.