Amazon Madison Mega Site is an operational AI data center in Canton, MS, USA, with AI chips owned by Amazon and used by Anthropic (speculative). It hosts an estimated 214k H100-equivalent chips, scaling toward a projected 514k H100-equivalent chips — supported by 284 MW of IT power, rising to 683 MW — at a capital cost of $10.8 B, rising to $25.9 B. We estimate that it uses Amazon Trainium2 chips. The timeline of IT power and compute capacity is based on satellite imagery, regulatory filings, chip efficiency, and third-party reporting. This site is likely part of the Anthropic–Amazon Project Rainier collaboration.