406 Area Code History

Counties in Montana within 406 area code include:
Beaverhead County, Big Horn County, Blaine County, Broadwater County, Carbon County, Carter County, Cascade County, Chouteau County, Custer County, Daniels County, Dawson County, Deer Lodge County, Fallon County, Fergus County, Flathead County, Gallatin County, Garfield County, Glacier County, Golden Valley County, Granite County, Hill County, Jefferson County, Judith Basin County, Lake County, Lewis and Clark County, Liberty County, Lincoln County, Madison County, McCone County, Meagher County, Mineral County, Missoula County, Musselshell County, Park County, Petroleum County, Phillips County, Pondera County, Powder River County, Powell County, Prairie County, Ravalli County, Richland County, Roosevelt County, Rosebud County, Sanders County, Sheridan County, Silver Bow County, Stillwater County, Sweet Grass County, Teton County, Toole County, Treasure County, Valley County, Wheatland County, Wibaux County, and Yellowstone County.