Here are the major airport frequencies for the Washington, DC area.
Ronald Reagan Washington National, DC (KDCA)
Potomac Approach 118.300 119.850 124.200 124.700 269.000 270.275 306.300 322.300 338.200 (124.200 269.000 East) (128.350 270.275 Southeast 3000 feet to flight level 190) (119.850 322.300 West) (118.300 306.300 Final East) (124.700 338.200 Final West)
Potomac Departure 118.950 121.050 125.650 126.550 257.200 269.500 343.700 348.725 (125.650 348.725 East 9500 feet and below) (126.550 269.500 East 10,000 feet to flight level 190) (118.950 257.200 West 9500 feet and below) (121.050 343.700 West 10,000 feet to flight level 230)
UNICOM 122.950
Washington Tower 119.100 120.750 257.600 120.75 (Copter)
Ground Control 121.700 257.600
Clearance Delivery 128.250
ATIS 132.650
Washington Dulles International, DC (KIAD)
ARMEL Radio 113.500T 122.100R
Potomac Approach 120.450 124.650 126.100 338.250 343.775 (126.100 338.250 331°-090°) (124.650 343.775 091°-240°) (120.450 343.775 241°-330°)
Potomac Departure 125.050 126.650 350.200 (126.650 121°-299°) (125.050 300°-120°)
UNICOM 122.950
Tower 120.100 125.800 128.425 317.800 348.600 (120.100 317.800 Runway 01R-19L) (128.425 348.600 Runway 01L-19R, 12-30)
Ground Control 121.900 125.800 132.450 317.800 348.600 (121.900 317.800 East) (132.450 348.600 West)
Ramp Control 129.550
Clearance Delivery 135.700 317.800
ATIS 134.850
