Organic Architecture is a design philosophy rather than a closed historical style; Wikipedia's own article states there are "contemporary creations of organic architecture" and that "the definition of 'organic' has dramatically changed during recent times," naming built examples as recent as 2023. Frank Lloyd Wright's own 1959 death is a candidate marker for the classic phase, but the philosophy itself is documented as continuing among later architects, so no single end year is supported by the source.
What would resolve this A conductor or taxonomy decision on whether an ongoing design philosophy like Organic Architecture should carry an end-year core key at all, or whether the key should be understood as not-applicable for a living philosophy with no closing event, distinct from a movement whose end is merely debated among several candidate years.
OpenArchitectural History / TaxonomyOrganic architecture (Wikipedia)