The main area codes used in the St. Louis area are 314 and 636.

The 314 area code is used in the City of St. Louis and the eastern part of St. Louis County, and it is recognized as the traditional St. Louis number. The 636 area code is primarily used in the western part of St. Louis County, St. Charles County, Jefferson County, and other suburban areas. Both area codes belong to the North American Numbering Plan (NANP), and even for local calls within the area, you must dial all 10 digits (including the area code) when calling a different area code. In the St. Louis metropolitan area, calls between 314 and 636 are often treated as local calls rather than long distance, but this can vary depending on the carrier plan, so it's important to check.

The major mobile carriers available in the St. Louis area are T-Mobile, AT&T, Verizon, and MVNOs like Boost Mobile and Cricket Wireless. In terms of coverage, Verizon and T-Mobile provide reliable 4G LTE and 5G services in both the St. Louis city and suburban areas. T-Mobile also offers 5G broadband (Home Internet) service in some parts of downtown St. Louis. Popular budget mobile services among the Korean community include Mint Mobile, which uses T-Mobile's network, Visible, based on Verizon's network, and Cricket Wireless, which operates on AT&T's network, all offering unlimited data plans at affordable rates ranging from $15 to $40 per month.

For wired internet services, Charter Spectrum provides the most extensive cable internet service in the St. Louis area. AT&T Fiber also offers gigabit fiber internet service in parts of St. Louis city and county, with coverage expanding recently. Spectrum's basic internet plan starts at around $50 per month (promotional period), while AT&T Fiber's gigabit plan is priced between $80 and $90. In some areas, competitors like Google Fiber and Sonic have also entered the market, increasing the options available. If you are planning to move or change your communication services, it is advisable to check the service availability at your target address on each carrier's website first.

Here is a summary of the phone number system for emergencies. The national emergency number for police, fire, and medical emergencies is 911. The non-emergency contact number for the St. Louis Metropolitan Police Department is 314-231-1212. The non-emergency contact for the St. Louis Fire Department is 314-622-4200. For Missouri state road traffic information and reporting, you can call 1-888-ASK-MODOT (1-888-275-6636). For utility-related emergencies such as electricity and gas, contact Ameren Missouri's emergency line at 1-800-552-7583. To report leaks to the St. Louis Water Division, call 314-768-6260.

Additionally, here is some practical communication information for Koreans living or doing business in St. Louis. In the early stages of immigration to the U.S., it may be difficult to sign up for a postpaid plan with major carriers due to a lack of credit history. In this case, starting with a prepaid plan can help build credit history for a later switch to postpaid. If you frequently make international calls, using internet-based calling and messaging services like Google Voice, KakaoTalk, and WhatsApp can significantly reduce communication costs with Korea. The Korean community in St. Louis often shares local information and living tips through KakaoTalk group chats, so participating in local Korean community channels early on can be helpful for settling in.