Kaplan spent most of his career teaching at the Conservative seminary, and Reconstructionism grew inside Conservative Judaism before separating from it. The institutional sequence runs: the Society for the Advancement of Judaism, founded in New York in 1922 after Orthodox rejection; Judaism as a Civilization, the movement's charter, published in 1935; a call for a seminary at a Montreal conference in 1967; and the Reconstructionist Rabbinical College, opened at Philadelphia in 1968. The college and the congregational federation merged in 2012, and the combined body renamed itself Reconstructing Judaism in 2018, noun to gerund, on the argument that the reconstructing is continuous.
Congregations are strongly lay-empowered, following Kaplan's principle that the community rather than the rabbi decides. The central body accordingly has less authority over its member congregations than the Conservative or Orthodox equivalents have over theirs.
Its most consequential decision came in 2015, when the rabbinical college voted to admit and ordain students in interfaith relationships, the first Jewish body anywhere to permit rabbis with non-Jewish partners. It drew condemnation from the other movements and some resignations from within, and it remains the sharpest boundary marker between Reconstructionism and Reform or Conservative practice. The reasoning is consistent with the rest: if the Jewish people is a civilization that people join, and if intermarriage is the ordinary condition of American Jewish life, then a rabbinate that cannot include it is refusing to serve the community it has.