Social networks such as Facebook allow libraries to be proactive in reaching their users. While some libraries have popular Facebook pages, it remains unclear what attracts users to these pages. This study evaluates relationships between libraries' Facebook page content and popularity. An analysis of 72 academic health sciences libraries' Facebook pages showed positive correlations between number of library fans and number of tabs, photos, events, and wall posts on Facebook. Libraries posting videos had significantly more fans than libraries without them. This study contributes to an understanding of correlations between content and popularity on Facebook, with implications for library outreach.