What is the value of a 1921 e pluribus unum silver dollar?

Answer 1

Not enough information. If you check your pocket change you'll see that EVERY U.S. coin carries that motto so it doesn't help to ID a coin. What matters is its condition and mint mark, and in this case its design. There were 2 different types struck that year, and they were made at multiple mints.

Please post a new question giving the coin's design - does it have the word PEACE on the back, or not? - and its mint mark, if there is one. Look for a D or S near the eagle's tail feathers; if you can't find it that's OK because not all silver dollars had mint marks back in those days.

U.S. minted 2 main types of silver liberty dollars for 1921 they all had E PLURIBUS UNUM on them, the Morgan and the Peace dollars.

First, the Morgan silver dollar was from 1878 to 1921 from various mints. There as, this Morgan could be worth from $30 to $1,000 depending on its mint mark and severe wear (Almost Good-1)or Brilliant Uncirculated (Mint State-65). A 1921-S (San Francisco) graded as MS-65 could be worth $1,000. If you believe you have a very high grade coin I recommend you have it graded by one of the top three unbiased graders for a fee.

Now for the Peace dollar, if you have a U.S. 1921 Peace silver dollar then this is better. This coin has the word "PEACE" in the reverse side below the eagle. A very limited number of 1921 Peace dollars were minted and without a mint mark. This could be worth from $95 to $2,000 depending on severe wear (Almost Good-1)or Brilliant Uncirculated (Mint State-65). If you believe you have a very high grade coin I recommend you have it graded by one of the top three unbiased graders for a fee.
For the year 1921, two different U.S. silver dollars were issued. Each is a separate series of dollar coins and the designs are very different. But because of the fact you included the motto E PLURIBUS UNUM (it appears on the front of the coin above Miss Liberty's head) in the question, the coin is a MORGAN dollar.

The 1921 Morgan dollars regardless of any mintmarks, are the most common of all Morgan dollars. Circulated coins run from $38.00-$40.00. Mint State are $48.00-$55.00 for most coins.