In a fairly worn condition, it is worth about $50. There are then 4 more
conditions of noticeable wear, with the first being called Very Good, the
2nd Fine, the 3rd Very Fine, the 4th is Extremly Fine (from there there is
About Uncirculated and in an Uncirculated State, there are 10 different
grades...60,61,62...70, but your note is likely to be in the first 4
Anyways, in VG it is $50, F is $70, VF is $90, XF is $110. There could
always be some interesting feature, ie, a low serial number, a rarer
stamp/seal, or a star note (if the serial number has 1 star and 1 letter and
the normal 8 numbers, instead of the common 2 letters and 8 numbers, this
can make it worth much more, although I can't say how much).
A note is only worth how much one can get for it. Post a picture and we can
tell you what it should be worth, or search eBay for some notes that are
being sold, search for just like 1917 VG, then 1917 F, 1917 VF, 1917 XF.
That should give you a pretty good idea of what each grade should like like,
and what your note is, and thus, it's value.
Personally, I don't have one of these, so I would keep it :)
1. 1917 $1 bill
2. 1917 $2 Bill