Affordable Care Act (ACA) Health Insurance Marketplace & Montana Medicaid Expansion enrollment assistance. Enrollment assisters from Blackfeet Community Hospital and Southern Piegan Health Center will be on hand to assist with enrollment. Blackfeet Community Hospital and Southern Piegan Health Center Benefits Coordinators will be available to assist with Medicare questions. Learn about Affordable Care Act Special Protections for American Indians Alaska Natives (AIAN). ACA Marketplace Health Insurance OPEN ENROLLMENT is November 1 – December 15, 2017. Note: Member of Federally Recognized Tribes may enroll in ACA Marketplace Health Insurance anytime during the year (not just the open enrollment period). Montana Medicaid Expansion: All individuals may apply for Medicaid at anytime.