In a 1 1/2- to 2-quart nonstick pan, combine rice, 2 1/4 cups milk, and cinnamon stick. Bring to a boil over medium-high heat, stirring, 10 to 12 minutes.
Add sugar, salt, and raisins. Simmer over medium-low heat, stirring often, until most of the milk is absorbed and pudding is creamy, 8 to 10 minutes longer.
Spoon into bowls and serve warm. Pudding thickens as it stands; if desired, stir in a little more milk.