Utilizing a historiographic approach based on Amazon’s Letters to Shareholders (LTS) over a twenty-year timeframe (1997–2016), this article identifies the discerning features of the company’s entrepreneurial culture that enabled it to become one of today’s most innovative organizations. A content analysis of the LTS while coding for underlying theoretical themes reveals Amazon’s entrepreneurial culture has been increasingly celebrating a spirit of “Self-Competition”, and by embracing ideas such as “Day 1 Mentality”, “Customer Centricity”, and “Human Capital Focus”. The study findings have useful insights for entrepreneurs, founding teams, and corporate managers engaged in developing an entrepreneurial culture within their own organizations.