Not yet reviewed by Pith; the record is open.

The Environmental Governance and Data Initiative (EDGI) regularly crawled US federal environmental websites between 2016 and 2020 to capture changes between two presidential administrations. However, because it does not include the previous administration ending in 2008, the collection is unsuitable for answering our research question, Were the website terms deleted by the Trump administration (2017--2021) added by the Obama administration (2009--2017)? Thus, like many researchers using the Wayback Machine's holdings for historical analysis, we do not have access to a complete collection suiting our needs. To answer our research question, we must extend the EDGI collection back to January, 2008. This includes discovering relevant pages that were not included in the EDGI collection that persisted through 2020, not just going further back in time with the existing pages. We pieced together artifacts collected by various organizations for their purposes through many means (Save Page Now, Archive-It, and more) in order to curate a dataset sufficient for our intentions. In this paper, we contribute a methodology to extend existing web archive collections temporally to enable longitudinal analysis, including a dataset extended with this methodology. We use our new dataset to analyze our question, Were the website terms deleted by the Trump administration added by the Obama administration? We find that 81 percent of the pages in the dataset changed between 2008 and 2020, and that 87 percent of the pages with terms deleted by the Trump administration were terms added during the Obama administration.