Preheat oven to 350 °F.
Combine the peaches, blueberries, 1 cup sugar, and water in a saucepan and mix well. Bring to a boil and simmer for 10 minutes. Remove from the heat.
Put the butter in a 9”x13” baking pan and place in oven to melt.
Mix together remaining 1 cup sugar, flour, baking powder, and salt. Add the milk slowly to prevent clumping. Pour mixture over melted butter. Do not stir.
Spoon the cooked fruit on top, gently pouring in the syrup. Sprinkle the top with ground cinnamon. Batter will rise to the top during baking.
Bake for 45 minutes until browned and sides pull away from the pan.
Serve with whipped cream or vanilla ice cream. Or my personal favorite is to pour cold milk over the warm cobbler and eat it like that.