Boil a large pot of water. Add your whole peaches and boil for one minute. Remove the peaches and immediately submerge them in ice cold water.
Peel the skin off the peaches. If your peaches are ripe, you can do this now with your hands very easily. If your peaches are under ripe, you might need to use a peeler.
Slice the peaches and add them to a large pot along with the juice of one lemon, sugar, and the salt. Allow it to sit for about 20 minutes for the juices to release from the peaches.
Heat the mixture until it comes to a light boil. Immediately turn it down so that it simmers. Any foam that forms on top can either be scooped out or mixed back in.
Cook, stirring frequently until the mixture is thickened. Mash the peaches to your desired consistency.
While your peaches cook, boil your canning jars for 10 minutes, and leave them empty in the hot water
Once the mixture is nice and thick, turn off the heat and stir in the vanilla.
Carefully ladle the jam into the jars and secure with your lids. Boil for 10 minutes.
Allow the jam to cool to room temperature before putting in your fridge,
*The exact amount of sugar you will need depends on how ripe/sweet your peaches already are! Once the peaches begin to soften, do a quick taste test to see if you need additional sugar. Remember, you can always add more sugar, but you cannot take it away!