Secretary of State: http://sos.mt.gov/

Contact info:

Phone: (406)444-3665
Fax: (406)444-3976
Email: [email protected]

Mailing Address:

Secretary of State
P.O. Box 202801
Helena, MT 59620-2801

Physical Address:

State Capitol, Room 260
1301 6th Avenue
Helena, MT 59620

Name search: http://app.mt.gov/bes/
Corporation and LLC forms: http://sos.mt.gov/Business/Forms/index.asp 
Filing fees: http://sos.mt.gov/Business/forms/fees/Business_Filing_Fees.pdf
Department of Revenue: https://revenue.mt.gov/
Department of licensing: http://onestoplicensing.mt.gov/