Wash, peel, and mash or purée the peaches.
Combine 1 cup peaches and 1 cup sugar in a large stock pot.
Bring the mixture to a boil, stirring constantly with a heat-resistant spatula. Boil for 4 minutes, or until the sugar dissolves.
Repeat the above (steps 2 and 3) three more times, adding the last 1 1/3 cups peaches and the last cup of sugar the last time.
Remove from heat and let the jam sit for about 10 minutes.
Skim any foam off the top of the jam in the pot.
Note: Your jam will seem more like syrup at this point. Please don’t be discouraged, because it works a little bit like magic from here on.
Pour the jam into a 9x13 cake pan, cover, and let stand for 3+ hours.* As it cools, it will begin to set and jell.
Decide whether you want to can or freeze the jam. The following instructions are for freezing.