After Dr. Montessori’s death in 1952, and the term “Montessori” became generic in the public domain, many independent organizations emerged, centered on various prominent personalities in the field. In 1971, for example, Dr. Helen Billings, a prominent American educator, developed an independent study course which gradually led to the formation of the “Montessori Institute of America” (MIA). Based in Kansas City, MO, the MIA affiliates training centers and provides membership recognition for its associated schools.
The “Pan American Montessori Association” was formed by Dr. Elizabeth Caspari and later brought under the direction of Dr. Feland Meadows, to provide teacher education and other support services in accordance with Caspari’s personal study and learning experience with Dr. Montessori.
The “International Association of Progressive Montessorians” (IAPM), founded by Sister Angela Martin, was fomed to provide its own distinctive certification and training of teachers as well as association of affiliated schools. These organizations have evolved their diverse forms of operation in the process of change over time, largely following the philosophical orientation of their principal founders.
In more recent times, with the growing use and influence of digital and computer technology,  many commercial and business interests arose to advance the marketing and public dissemination of Montessori education, each according to its own particular philosophical and business interests and orientation. For example, Tim Seldin, a former vice-president of the AMS organization, left that organization in the 1980’s, to pursue his ideas and business interests in the field through his organizations, the “Montessori Foundation” and “International Montessori Council.”
Among these organizations, some follow the “personality” of its founder or leader, while others take on the philosophy of the surrounding “culture,” company, or business community served by its activity in the field.