Phase I Environmental Site Assessment (ESA) reports provide historical overviews of contaminated sites and are often key resources in environmental and toxic tort litigation. However, despite the requirement that they meet set standards, in reality, ESAs often have certain limitations when it comes to historical analysis. Historical research, a required component of ESAs, is often extremely basic and sometimes conducted by personnel without extensive training in historical research methodology. In our experience, ESAs typically check all of the required boxes for historical research but seldom go deeper, consequently leaving out critical historical information. This has proven especially true for properties active prior to the 1970s, or with complicated owner/operator histories. From minor errors in dates and names to misidentification or omission of potentially responsive parties (PRPs), there are possible risks in relying on the incomplete picture typically provided by an ESA.