Get a local business phone number in Monmouth, IL

What area code is Monmouth, IL?

Monmouth township is a Census town in Warren County, Illinois, with an estimated 9,628 residents in 2024. All 8 exchanges NANPA lists for its rate center are in area code 309. 309 is part of an overlay with 861, so a new local number in Monmouth may carry any of those codes depending on which have numbers available. Monmouth is in the Central time zone.

According to NANPA's dialing-plan data, local calls within 309 are dialed as ten digits (area code plus number) and toll calls as 1 plus ten digits.

Who holds Monmouth phone exchanges

7 carriers hold the 8 exchanges assigned to Monmouth's rate center. Citizens Telecom CO Illinois-frontier Citizens -il has the most, with 2. 5 of them are pooled codes, which the holder shares with other carriers in blocks of 1,000 numbers. A business number in Monmouth can come from any of these blocks; once it is yours, porting lets it move between providers.

Monmouth phone prefixes

These are the central office codes NANPA records for Monmouth. A caller seeing one of them recognizes a local number. The earliest assignment date recorded in the file for these codes is 2003. 3 of the 8 were assigned in 2020 or later.

When Monmouth's exchanges were assigned

The table groups Monmouth's exchanges by the decade NANPA recorded them as assigned.

Rate centers and local calling in Monmouth

Phone numbers are tied to a rate center, the local calling area used to decide whether a call is local or toll. Monmouth's numbers are rated to the MONMOUTH rate center in NANPA's records. A business number from one of the prefixes above shows up on customers' phones as a Monmouth number.

If your business already has a Monmouth number, porting it to Callata is free and keeps it on your cards, listings and vehicles.

Businesses around Monmouth

Monmouth is outside any Census metro or micropolitan area, so the figures below are statewide. County Business Patterns counted 322,415 business establishments in Illinois in 2023, employing 5,661,761 people. The largest sectors by establishment count are professional, scientific, and technical services (37,946), health care and social assistance (37,597), and retail trade (35,801).

A Monmouth number on Callata

For $99 a month, Callata puts a team of up to 5 on one plan ($20 for each person after that): up to 3 local numbers, unlimited inbound calls, a pooled allowance of 1,500 outbound US and Canada minutes per user, browser and cell calling, voicemail transcription with urgency triage, recorded calls with AI summaries and business-hours routing, with E911 on every number.

Porting a number you already use in Monmouth is free, and business texting is available once the carrier registration (10DLC) is approved; the registration carries a one-time $49 fee. Which specific numbers are open in a given area code depends on carrier inventory at the time you sign up.

AI agents are optional: an AI receptionist or scheduler can pick up when the team is busy or closed, take a message, send a text or email, or transfer the call. They draw on prepaid AI minutes ($0.25/minute), disclose that they are AI, and outbound AI calls require prior consent and are limited to 8am–9pm.

Per-seat phone plans multiply by headcount. For the rounded average establishment size in Illinois, 18 users on RingCentral RingEX Core come to $540.00 a month and on Ooma Office Pro $449.10, at month-to-month list prices checked September 28, 2026. Callata comes to $359.00 a month for 18 users ($99 a month with 5 users included, then $20 per additional user), below both.