Building Software Product Lines (SPLs) from existing artefacts is known as the extractive approach for SPL adoption. The traditional case is that variants are created with ad-hoc reuse (e.g., copy-paste-modify to quickly respond to different customer needs) and practitioners want to reengineer them to an SPL. Several industrial cases have been presented in the literature to motivate the interest of the extraction and many case studies are used to validate methods and techniques for different activities during this adoption process. However, there is no catalog or repository that gather together case studies and artefacts related to extractive SPL adoption. In this paper we present ESPLA, a catalog of Extractive SPL Adoption case studies that aims to foster the advance of this field by providing comprehensive information about case studies that will be otherwise scattered in the literature. Researchers, practitioners and educators can use this catalog to find the case studies that better fit to their particular needs. Currently, ESPLA contains information about 123 case studies and it is intended to be a catalog that can be updated and extended by the community.