2 cents in the U.S.
The price of a First Class Stamp in the US in 1920 was 2 cents. It was good for one ounce of First Class Postage. It went up to 3 cents in 1932.
Four cents for a one ounce First Class letter.
The postage rate for a standard First Class letter was 2 cents in 1920.
Gerhard Stamp was born on 1920-06-03.
One cent
in 1921 eggs were 47cents,I found this by reading a magazine called Reminisce,it was very interseting to see how prices were in 1921,you could by peanut butter for 15cents a pound,and a first class stamp for 2 cents.
In the 1920's you could by a stamp for 1-3 cents a stamp.
You will have to identify what stamp you have as there were many issued or available in 1920. Consult a catalog, Gibbons or Scott to identify the item you have. It will also provide an estimated value for you.
But it's a bit of a challenge to answer your question because I'm guessing some of us are not sure about: the country you could mean (U.S.? Turkey? Russia? Canada?), the time reference you may mean (the first black artist? 1920's? Currently? etc); and what you mean by artist. If you are speaking of the U.S. AND if you are asking who the first Black person was to be featured on their postage stamp, then your answer is Booker T. Washington. Romare Bearden, an African-American has his works featured on a recent set of 4 Forever Stamps.
Depending on which of the one dollar stamps you have, it could be worth a great amount of money. One dollar stamps have been issued since 1892 when a $1 commemorative stamp (Scott #241) was issued. This beautiful showed Isabella Pledging Her Jewels to help Columbus finance his trip to the new world. If THIS is the stamp you have, then is is worth over $2,500 in MNH condition.
Scott US 2256. The stamp is not from 1920, that is the era of the wheel chair pictured. It can be purchased mint for 80 cents and used for 20. A dealer is not likely to want to purchase a single copy.
As far as I know, Eugene Debs has never appeared on a US postage stamp... it would be only marginally less odd than putting, say, Josef Stalin on one.(For those who don't know who Debs was: he was the presidential candidate of the Socialist party back around the time of World War I. Debs was actually in prison at the time of his 1920 presidential bid.)