Cream shortening in a medium mixing bowl; add 3/4 cup sugar and egg, beating well. Add milk, and beat well. Combine 2 cups flour, baking powder, and salt; add to creamed mixture, mixing well. Fold in blueberries. Spread mixture into a greased and floured 13- x 9- x 2 - inch baking pan.
Combine remaining sugar, flour, and cinnamon in a small mixing bowl. Cut in butter with a pastry blender until mixture resembles coarse meal. Sprinkle over blueberry mixture in pan. Bake at 375° for 45 minutes. Cool. Cut into squares to serve.