Face value is $20. It's value to a collector will depend on the series, signatures, and condition.
Face value only.
US $2 Federal Reserve Notes printed since 1976 are generally only worth face value in circulated condition. An uncirculated 2003 note might retail for all of $3.
Face value if worn, up to maybe $70 if very little wear is apparent.
Priceless. The first Federal Reserve Notes were printed in 1914.
Unless it's uncirculated, maybe $1.10. A dealer will pay face value.
A denomination is needed. Please look for questions in the form "What is the value of a 1928 A US [denomination] dollar Federal Reserve Note?" for specific information.
The only Federal Reserve Notes dated 1976 are $2 bills. In circulated condition they have no added value.
$22 to $28 at retail. A dealer will pay close to face value only.
In worn condition, face value only. If only slightly worn, $8 or so.
$1 Federal Reserve Notes have been printed since 1963 so a date is needed. However, nearly all of them are very common and are worth either face value or a only slightly more.
You didn't specify the bill's denomination, but most bills printed in the 1960s and later are only worth face value.
In uncirculated condition it might retail for $12. If it has any wear, it's only worth face value.