  I review the history and development of Modified Newtonian Dynamics (MOND)
beginning with the phenomenological basis as it existed in the early 1980s. I
consider Milgrom's papers of 1983 introducing the idea and its consequences for
galaxies and galaxy groups, as well as the initial reactions, both negative and
positive. The early criticisms were primarily on matters of principle, such as
the absence of conservation laws and perceived cosmological problems; an
important step in addressing these issues was the development of the
Lagrangian-based non-relativistic theory of Bekenstein and Milgrom. This theory
led to the development of a tentative relativistic theory that formed the basis
for later multi-field theories of gravity. On an empirical level the predictive
success of the idea with respect to the phenomenology of galaxies presents
considerable challenges for cold dark matter. For MOND the essential challenge
remains the absence of a generally accepted theoretical underpinning of the
idea and, thus, cosmological predictions. I briefly review recent progress in
this direction. Finally I discuss the role and sociology of unconventional
ideas in astronomy in the presence of a strongly entrenched standard paradigm.
