Combine first 4 ingredients in a bowl. Cut shortening and butter into flour mixture with a pastry blender or fork until mixture is crumbly. Stir in raisins.
Whisk together milk, eggs, and vinegar; add to flour mixture, stirring just until moistened. Pour batter into a greased 10 1/2-inch cast-iron skillet.
Bake at 350° for 35 to 40 minutes.
NOTE: Bread also may be baked in 2 greased 8-inch round cakepans for 30 to 35 minutes.