In a 20-year period, AR has gone from being viewed as a heavyweight technology to a new medium for a variety of applications. As a result there has been an increasing need for tools to support AR design and development that fully address the needs of non-technologists. From my AR research, I learned that three critical components for these authoring tools are support for an established content pipeline, rapid prototyping, and user experience testing. The history of media teaches us that AR also shares underlying technologies with a variety of more mature media such as film, VR, and the web with existing workflows and tools. Therefore, we created an AR authoring tool that supported these three critical components, and whose design was informed by established approaches in these related domains, allowing developers with a range of technical expertise to explore the AR medium. In this dissertation I present four main contributions. The first was an exploration of the AR design space focused on close collaboration with designers. This work resulted in guidelines for AR authoring tools, and informed the development of the Designer's Augmented Reality Toolkit (DART). These guidelines were validated via internal and external projects. A qualitative study of long term DART use that provided insight into the successes and failures of DART as well as additional understanding of AR authoring needs. Lastly, I trace two main threads to highlight the impact of this work, the development of the AR Second Life system and the creation of the Argon AR web browser.