In order to increase the understanding of the diversity, distribution and abundance of liverworts and hornworts on the Atlantic Coastal Plain, a six year study (2004–2009) was conducted focusing on the Delmarva Peninsula (a land mass comprising portions of the states of Delaware, Maryland, and Virginia). Our previous knowledge of the liverworts and hornworts of the Delmarva were minimal. Collections were few and usually localized, and published and unpublished reports were scarce. Results from this study are presented in the format of an annotated checklist and represents the first comprehensive study on the liverworts and hornworts of the Delmarva Peninsula. A total of 65 species, subspecies, and varieties were documented during this study with 22 being reported as new to the bryoflora of the Delmarva.