What is the value of a 1900 US half dollar?

Look on the back of the coin to see if there's a small mint mark letter below the eagle. It may be blank or there may be an O or S.

Numismedia lists the following approximate retail values as of 04/2011:

No mint mark (Philadelphia):

Very worn condition - $17

Moderately worn - $38

Slightly worn - $91

Almost no wear - $338

Uncirculated - $480 to $16,250 depending on quality

"O" mint mark (New Orleans):

Very worn - $18

Moderately worn - $61

Slightly worn - $168

Almost no wear - $450

Uncirculated - $860 to $29,250

"S" mint mark (San Francisco):

Very worn - $17

Moderately worn - $54

Slightly worn - $110

Almost no wear - $382

Uncirculated - $600 to $31,850

DISCLAIMER: The retail values quoted are the best available as of the date shown, but may vary significantly due to changes in the precious metals market. Also the wholesale (buying) price of a coin will be less than the selling (retail) price. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.

1900 Barber or Liberty Head Half Dollar: With no mint mark, in good condition is worth $6.50, uncirculated is worth $400.00, proof is worth $700.00. With O mint mark, in good condition is worth $7.00, uncirculated is worth $650.00. With S mint mark, in good condition is worth $7.00, uncirculated is worth $550.00.