The MBCA, as it is usually known, is a model statute that suggests a corporate law regime for state governments to adopt. About 35 U.S. states have corporate laws based on the MBCA.
The MBCA's predecessor, the Uniform Business Corporation Act (UBCA), was first drafted by the National Conference of Commissioners on Uniform State Laws (NCCUSL) in 1928. The NCCUSL had previously had great success in the Uniform Partnership Act and Uniform Limited Partnership Act, which every state in the U.S. adopted verbatim. The UBCA wasn't nearly as popular: only four states adopted it.
In 1943, the American Bar Association's Committee on Corporate Laws began circulating a draft Model Business Corporation Act largely based upon the corporate statutes of Illinois. The NCCUSL renamed its statute "Model Business Corporation Act" around the same time, so for a few years there were actually two MBCAs. However, the NCCUSL withdrew its MBCA in 1958, after the ABA's version began gaining popularity.
The MBCA is revised every year, and proposed revisions are published in the ABA's Business Lawyer magazine. Of course, revisions to the MBCA take on no legal force until they are adopted by states.
The most recent major change to the MBCA was in 1984. About twenty-five states have adopted the 1984 MBCA; a few others continue to survive with statutes based on older versions of the MBCA, mainly the MBCA of 1969. MBCA states include Arizona, Florida, Georgia, Illinois, North Carolina, South Carolina, Washington, and Wisconsin.
In law schools, corporate law courses are usually based on the MBCA. However, the MBCA has only limited applicability. About half of the companies on the Fortune 500 list are set up under the Delaware General Corporation Law, which is completely different from the MBCA in content and structure. Law students therefore learn Delaware provisions alongside MBCA provisions where the two differ most from each other.
Besides Delaware, many other states that house a lot of big companies, including New York, California, Texas and Illinois, have corporate statutes that combine MBCA and Delaware influences with local rules: they can get away with this because their local bar associations are big enough and influential enough to address legal issues on their own, rather than simply adopt the views of the ABA. The MBCA in its purest incarnations is mainly confined to smaller states which have better things to do with their free time.