Stampless Cover… 1804?

This is a letter to the Honorable Judge Wilson. I believe it says Clermont on the bottom right. An Internet search leads me to a William Wilson of Clermont Columbia County New York. This man was apparently both of position and the judge, and even a postmaster.

Could this really be THAT OLD?

Very likely that old. I await answers from others with much more knowledge than me.

Yes. New York City markings go back to at least 1710. 1804 was the first year for the circular postmark. The city used lots of different straightline handstamps in the 18th century, then a fancy "clamshell" marking in the 1798-1804 period (I've sold 10 or so of those in the last 3 months); there was also a small oval handstamp in the 1802-1804 time frame.

Any idea of value? There isn't really any indication of cost to sender.

There is. It was 12 1/2 cents (the rate for mailing a single sheet 90-150 miles at the time); that appears at the upper right of the cover. It was not mailed prepaid, so the payment would have been due by the recipient. Prior to 1845, rates were a combination of distance and number of sheets of paper; in 1845 this changed to weight and distance. There wasn't a truly "flat" domestic letter rate (3 cents per ounce, any distance) until 1863.

Prepayment was optional on letter mail until 1855, and prepayment by stamps was not required until 1856.

Good chance to note that the American Stampless Cover Catalog is available at no cost in the electronic library of the United States Philatelic Classic Society. The front matter of volume I of the catalog includes quite a bit of information about postal rates, among other things.