After the 4th, the stands would have a closeout sale and we would buy up huge quantities. No one cared about sparklers, of course. Firecrackers of decent size were always gone, but ladyfingers and bottle rockets could be had ridiculously cheap.
Kept us in stock for a few months.
In the 1940s, we used to make our own explosives (salt peter, sulfur and charcoal ground up together). Got the formula from the family’s 11th edition of the Encyclopedia Britannica. A kid could buy potassium nitrate then at the local drugstore ... made firecrackers out of toilet-paper rolls wrapped with layers of glued string which made an impressive pop.