This collection contains soil samples collected from the megapit at each terrestrial site (NEON sample class: mgp_perarchivesample). During the construction of all 47 terrestrial field sites, "Megapit" soils were collected from multiple horizons at a single soil pit that was up to 2m deep. These samples serve as a reference of soil physical and chemical conditions at the time the NEON site was constructed. The Megapit Archive is curated at the NEON program headquarters in Boulder, CO. Megapit soil samples are available upon request (https://www.neonscience.org/samples/soil-archive).