Among the different stores you can find postage stamps in, Walgreens is probably one of the last places you would look into. However, as surprisingly as that may sound, this pharmacy chain is one of the longest standing stamp suppliers in the USA.
They offer a wide variety of stamps that are sure to suit all your mailing needs. If you do not find them in the aisles, ask the clerk at the counter as they often keep them behind the counter to avoid damage. Just like at Walmart, at Walgreens you may purchase single stamps as well as stamps in bulk, but you should always specify the kind of stamp you need as there are different ones, with different prices, for postcards, international mailing and shipping, priority mailing and shipping, and so on.
The prices of the stamps you will find at Walgreens are equal to the ones you will find on the official USPS website and at the post office; a postcard stamp costs $0.34, a First Class Mail stamp costs $0.49, and the “additional ounce” stamp costs $0.21. If you mail or ship often, you may want to invest in a bulk purchase of stamps, in which case you should ask for either a strip (10 stamps), a sheet (12, 16 or 20 stamps), a book (20 stamps) or a roll (100 stamps) of stamps, if you have questions about where to buy stamps read linked article.
Unfortunately, the Walgreens website does not offer online stamp shopping so you may have to take the time to actually go and visit the pharmacy. Alternatively you can buy them in walmart online shop because walmart sell stamp or you may wait for the next time you have to replenish your medicine cabinet and take that occasion to enquire about the type of stamps the Walgreens closest to you offers.