Prep your jars and lids before getting started. Scrub them thoroughly with hot soapy water, give them rinse and then pat them dry.
Wash the peaches, remove the skin*, slice them in half, and remove the pits. Peeling them is optional, but I don’t really like the skin in my jam.
Puree your peaches in a blender, or mash them up with a potato masher if you don’t have a blender. They should resemble a fairly thin pulp.
Combine a cup of peaches and a cup of sugar in a tall large stock pot, so the mixture doesn’t boil over when it foams up.
Bring to a boil, stirring constantly. Boil for 4 minutes while still stirring until the sugar is totally dissolved.
Repeat this process 3 more times, adding the remaining peaches and sugar in stages to keep the pot boiling. You'll add the final 1 1/3 cups peach puree and the final cup of sugar the last time.*
Remove the mixture from the stovetop once you’ve cooked down all of the peach puree and sugar. Let it rest for a few minutes, and then skim off any foam that forms on top.
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 into a 9×13 cake pan and cover with plastic wrap. Let it sit 6-12 hours at room temp to set and jell.*
Decide whether you want to can* or freeze the jam. The following instructions are for freezing.