The Guccion Biorepository is the singular work of Dr. John Gregory Guccion (1936–2025). A US medical pathologist and pioneering electron microscopist, he was a life-long botanist who amassed an unparalleled biorepository of ~68K specimens over > 70 yrs. GUCCI is among the largest, most comprehensive baselines of Mid-Atlantic plant and fungal species occurrences for 1970–2000. The unique data it contains complement those from existing biorepositories and fills significant sampling gaps: in time, space (numerous locations not studied previously or since) and organisms (>50% of the occurrences are lichens). Its salvage, curation and distribution to collaborating herbaria is funded by the US National Science Foundation (#2628743, #2628744).