In a large bowl, combine peaches, brown sugar, flour, and cinnamon. Toss together until peaches are coated and no clumps remain. Set aside.
In a separate large bowl combine the white whole wheat flour, sugar, cinnamon and salt. Mix with a fork. Then add the butter and maple syrup. Mix until pea-sized pieces form. I find it easier to use (clean) hands over a utensil. The dough should be able to stick together.
Press about ⅔ of the dough into an 8-by-8-inch baking pan lined with parchment paper.
Pour the peaches over the crust. Distribute evenly so no obviously large empty pockets remain.
Crumble the remaining dough over the peach filling.
Bake for about 30 minutes, until the top is golden brown.
Let the bars cool before cutting. Best stored in the fridge for up to one week.