In large bowl, with mixer at low speed, beat butter and 1 cup sugar just until blended. Increase speed to medium; beat until light and fluffy, about 5 minutes.
Meanwhile, in medium bowl, combine flour, baking powder, and salt.
Reduce speed to low; add eggs, one at a time, beating after each addition until well blended, occasionally scrapping bowl with rubber spatula.
Alternately, add flour mixture and milk, mixing until just blended.
Gently stir in blueberries.
Spoon the batter into loaf pan.
Bake 1 hr and 5 minutes or until toothpick inserted in center, comes out clean.