Developmental disabilities are a diverse group of severe chronic conditions that are due to mental and/or physical impairments. People with developmental disabilities have problems with major life activities such as language, mobility, learning, self-help, and independent living. Developmental disabilities begin anytime during development up to 22 years of age and usually last throughout a person’s lifetime.
MRDD or MR/DD, short for Mental Retardation and Developmental Disabilities, refers to services designed to assist mentally and developmentally challenged people and their families. In the United States, this term is used by state and local government agencies that receive federal funding under Title XIX of the Social Security Act of 1965.

The State of Ohio created county boards of mental retardation in 1967 with the passage of Ohio Amended Senate Bill 169. The county boards became known as “169 Boards.” When the first Board was installed in 1967, it continued to contract with the  Hamilton County Welfare Department (HCWD) to provide the same services the department had provided for several years. In 1971, however, the Board began initiating and administering its own programs. In  1980 the scope of county boards was broadened through passage of Amended Substitute Senate Bill 160, which updated and clarified the duties and responsibilities of the county boards, and added  developmental disabilities to the Board’s title. The growth of programs, both in size and numbers, has been phenomenal.

The Arc of the United States is the world's largest grassroots  organization serving people with intellectual and developmental disabilities. The organization was originally founded in the 1950s by parents of individuals with developmental disabilities. It was originally called  the Association of Retarded Children, but it has since expanded its function and subsequently changed its name. Since its origination, the organization has established state chapters in 39 states, with 730 local chapters in states across the country. The Arc of the United States is based in Washington D.C. The mission of The Arc is to “promote and protect the human rights of people with intellectual and developmental  disabilities and actively support their full inclusion and participation in the community throughout their lifetimes.”