In saucepan, combine sugar, corn syrup, milk, and salt. Bring to boil, stirring until sugar dissolves. Cook to soft ball stage (236 degrees) or until small amount forms soft ball when dropped in cold water. Remove from heat; add vanilla and peanut butter. Cool approx.15 minutes or until lukewarm. Beat vigorously with wooden spoon until mixture is creamy and begins to thicken. Turn into buttered loaf pan, or pour onto buttered plate. Cool before cutting into squares. YIELD: 1 pound.