Seems from the number of posts that you have a rather large accumulation which was not well identified. If you want to learn more about these stamps, I highly recommend the Micharelli Identification Guide. It will help you go through all the stamps prior to the 1938 Presidential Series, as far as regular issue stamps are concerned. In case you don't know what I'm referring to, postage stamps are generally - in the U.S. - either printed in large quantities for extended periods of use (these are regular issues) or in smaller (but still very large) quantities for a limited period and to commemorate a specific event, date, or person. These are called commemorative stamps.
The aforementioned guide deals with the identification of the regular issues which can be rather intimidating and confusing until you realize there's really a few keys to identifying them. You can get a copy of it from many stamp dealers, on line (I believe Amos Press may carry it) and from
ebay.
Good luck!