GMS (Group Main Stream) was founded in 1980 by a group of concerned people who recognized the need for services for persons with intellectual disabilities and Autism.

Established in 1959, Uplift, Inc. has been providing services within the community for more than sixty years. Dedicated to the provision of quality services, a strong tradition of leadership has continued throughout our history. Uplift has evolved into an agency which provides residential, integration, and employment services to adults with disabilities whose needs are such that they require specialized supports.

Independence Advocates of Maine (IAM) started in 1977 with a big dream: to help people with disabilities live their best, most independent lives. IAM began as a single program, Treats Falls House, an ICF/IID supporting people with exceptional medical needs.  Over time, our programs expanded to include residential support (group homes, independent living, shared living), community support, employment support, and enabling technology.

In 2024, the leaders of these respected agencies began discussions about how they could better serve people with intellectual and developmental disabilities by combining their strengths. These conversations led to the formation of 3Rivers in 2025, a unified organization committed to providing high-quality, person-centered support.