49 CFR 366.4: Required States.

(a) Every motor carrier, except a motor carrier operating exclusively in Alaska or Hawaii, must designate process agents for all 48 contiguous States and the District of Columbia, unless its operating authority registration is limited to fewer than 48 States and DC. When a motor carrier's operating authority registration is limited to fewer than 48 States and DC, it must designate process agents for each State in which it is authorized to operate and for each State traversed during such operations. Every motor carrier operating in the United States in the course of transportation between points in a foreign country shall file a designation for each State traversed. Every motor carrier maintaining a principal place of business and operating exclusively in Alaska or Hawaii must designate a process agent for the State where operations are conducted.

(b) Brokers. Every broker shall make a designation for each State, including DC, in which its offices are located or in which contracts will be written.

(c) Freight forwarders. Every freight forwarder shall make a designation for each State, including DC, in which its offices are located or in which contracts will be written.