Abstract
This study is a quantitative analysis of the microblogging site Tumblr in order to determine how this platform is currently being used by libraries and special collections/archives in the United States. Data on library Tumblr blogs was collected at three points during a one year period and included library type, start date, number of posts, average posts per day, type of post, as well as other descriptive information. There is a growing library presence on the social media site Tumblr. The results shows adoption of the social media platform by multiple library types: academic, public, special collections/digital libraries, library organizations and other library/archives.