Boil potatoes 7 to 8 minutes or until just barely tender. Drain, let cool, and slice thinly.
Cook bacon and crumble. Set aside.
Roll out dough. You want it to be rather thin but not so thin it falls apart. Roll half the dough into a 10 to 12 inch circle and place in the cast iron pan (you will do this twice if you want two pizzas unless you have 2 pans!)
Brush a touch more olive oil over the top of the dough
Spread 3 to 4 TBSP of the ranch dressing over the dough
Lay the slices of potato over the ranch dressing and sprinkle with half the bacon.
Top with half the shredded cheddar (just over 1 cup)
Bake at 500 degrees for 12 to 15 minutes or until crust edges are lightly brown and cheese is bubbly and starting to darken
Remove from the oven and let cool slightly before removing the pizza from the pan.