Postmortem brain tissue and donor metadata were obtained via the UW BioRepository and Integrated Neuropathology (BRaIN) laboratory from participants in the Kaiser Permanente Washington Health Research Institute ACT Study and the University of Washington ADRC. The study cohort was selected based solely on donor brains undergoing precision rapid procedure (optimized tissue collection, slicing and freezing) during an inclusion time period at the start of the SEA-AD study, excluding those with a diagnosis of frontotemporal lobar degeneration, Down syndrome, amyotrophic lateral sclerosis or other confounding degenerative disorder (not including Lewy body disease, limbic-predominant TDP-43 encephalopathy or microvascular brain injury). The cohort was chosen in this manner to represent the full spectrum of AD neuropathology, with or without common comorbid age-related pathologies. No randomization was used in cohort selection. The experimental donor cohort contains 84 donors, 51 females and 33 males, aged 65–102 (mean 88). The 84 donors span the spectrum of AD pathology, from those without AD/dementia to those with dementia and high AD pathology. More information available at SEA-AD.org.