North Dakota, Minnesota

Dakota Central Telecommunications (OCN 1610 and 1683) has company-wide local calling – not sure when this took effect. Source: DCT
Dickey Rural Networks (OCN 1611) also has company-wide local calling as of 2013-12-01. Source: DRN
Farmers Mutual Telephone Company (OCN 1389 and 2836) and Federated Telephone Cooperative (OCN 1390, 1403 and 2629) have formed a partnership known as Acira, with company-wide local calling among members of both companies. Source: Acira