This dissertation examines the use of social media technologies by US local governments for internal and external collaboration. Collaboration is defined as the process of working together, pooling resources, sharing information and jointly making decisions to address common issues. The need for greater collaboration is evident from numerous examples in which public agencies have failed to effectively collaborate and address complex challenges. Meanwhile, the rise of social computing promises the development of ‘cultures of participation’ that enhance collaborative learning and knowledge production as part of everyday work. But beyond these gaps and expectations, there has been little systematic empirical research investigating the use of these powerful and flexible technologies for collaboration purposes. In line with prior research, my dissertation draws on sociotechnical and resource dependence theoretical approaches to examine how the interaction between technological and social context of an organization determine the adoption and use of a technology for a task. However, in a break with prior work that often aggregates social media technologies as one class of technology, this dissertation theorizes different classes of social media based on their functionality and purpose. As a result, it develops more explicit means by which organization, technical, and environmental context matter for effective collaboration. Based on the aforementioned theoretical approaches, the dissertation develops a theoretical model and several hypotheses, which it tests using a unique 2012 national survey of local governments in the US conducted by the Center for Science, Technology and Environmental Policy Studies at ASU. Overall, the findings of this dissertation highlight that the adoption and use of social media technologies for collaboration purposes can be understood as an outcome of stakeholder participation, innovativeness, and social media type. Insights from this dissertation contribute both to our theoretical understanding about social media technology adoption and use in government and provide useful information for agencies.