From the website of the Metropolitan Police Department:

Whether you're celebrating Independence Day or the New Year, a backyard barbecue or other family occasion, it is important to understand the laws regulating fireworks use in the District of Columbia. Find out what fireworks are permitted and prohibited in DC.

Prohibited

Article 27, DC Register, F-2700.1.1: The manufacture, storage, display, sale, setting off, or discharge of any firework listed below is prohibited in the District of Columbia.

• Firecrackers of any kind or description

• Any firework that explodes, such as cherry bombs, salutes, Roman candles, floral shells, artillery shells

• Any firework intended to move after the piece is placed and fired; such as bottle rockets, parachutes, buzzbombs, pinwheels, helicopters, jumping jacks

• Sparklers more than 20 inches (50mm) in length

• Any firework that contains mercury, arsenic, tetryl, phosporous, sulphocyanide, magnesium, potassium picrate, gallic acid, chlorate of potash and sugar, or any highly oxidizing agent

• Any firework having a side fuse, or a fuse inserted at any point along the length of the firework

• Any firework found by the code official to be dangerous to the safety of persons or property
  

Permitted 

Article 27, District of Columbia Register, F-2700.1.2): The fireworks listed below are permitted to be stored, displayed, sold, delivered, used, and possessed in accordance with the provisions of this article.

• Any firework specifically excepted in this article

• Toy paper caps containing not more than twenty-five hundredths (0.25) of a grain of explosive composition per cap

• Sparklers not more than 20 inches (50mm) in length

• Torches, cones

• Box fires, fountains

• Dip-sticks, non-poisonous snakes

• Paper novelty items, colored lights

And here is a handy info sheet you can download and print: