In 1969, the Missouri State Legislature passed Senate Bill 40, enabling legislation (205.968 through 205.972 RSMo.) that is designed to allow individual counties in Missouri to approve a property tax levy to provide support to persons with intellectual and developmental disabilities in areas of residential, employment, and related services.  This tax levy is administered by a local county board that is commonly referred to as a Senate Bill 40 board, an SB40 board, a county board, or a developmental disability resource board.

Organized in 1979, the Missouri Association of County Developmental Disabilities Services (MACDDS) provides a strong forum to share information, discuss common problems, and act cohesively in areas of overall concern.  The membership meets monthly to focus on best practices and enhance the leadership skills of its members.  Each year the Association sponsors a fall conference that, through a series of workshops, seeks to bring together technical assistance and innovative ideas to broaden the perspective of member counties, related private organizations, and affiliated public agencies as they endeavor to serve people of Missouri with developmental disabilities.

MACDDS continues to have a strong impact on legislative initiatives. Because of the pleasant blend of urban, suburban, and rural member counties, each MACDDS representative reflects the collective political strength and determination of those county voices.  MACDDS supports providing people with developmental disabilities with individualized, quality services in their community of choice.  MACDDS recognizes and promotes the individuality and autonomy of local county SB40 boards in the provision of supports based on the unique needs of their communities.