Area Code 303 was proposed in 1947 for serving the entire State of Colorado - State of United States. The code 303 is one of the eighty six original area codes which were proposed for USA by NANPA (North Numbering American Plan Administration). The particular code shares its geographical boundary with area code 720. Both these area codes are overlaid areas and are serving several areas located within the State of Colorado.
Ten digit dialing is mandatory for connecting to exact destination within the service area -- even while making a local phone call. Entire State of Colorado was served by area code 303 until 1988 when the code 303 got a split because of the population growth and shortage of available phone numbers. As a result code 719 was created on 5th March 1988. Later on, in 1995, telephone code 303 split off again and gave birth to new area code - 970. The 303 area code was overlaid by the code 720 on 1st June 1988. Standard Time Zone followed by the code 303 is Mountain Time Zone.
The State of Colorado is served by total four area codes:
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