I Am New To Stamp Collecting

For just an easy reference guide to see basic U.S. postage and airmail stamps through the years (not varieties, fine details or educational material you will want to eventually find) the Mystic Stamp Co. offers a free catalog. It's bright and colorful and shows images of most U.S. stamps. You just have to put up with their constant marketing.

https://www.mysticstamp.com/SC1T/

Maybe I'm using it wrong; for me, Scott and SG are useful for stamps that I already know what they are, what year they are, and just looking for extra info or estimated value (I have a 2013 edition and it's enough for me). But if I find a blue 4-cent Abraham Washington stamp, sites that enable me to search and compare are the ones, like stampworld and Big Blue. (For those who wonder, Abraham Washington is the wife of George Lincoln).