Precise time and location are at the core of many Cyber Physical Systems (CPS) applications, as can be seen by the impact of the Global Positioning System. Indoor<br>localization systems will enable applications ranging from navigation, asset tracking and secure device interaction to mixed reality experiences and emergency support<br>(e911). However, indoor environments are full of barriers, which attenuate and scatter signals that make it challenging to provide high coverage in a cost-effective and reliable manner at scale. In this dissertation, we will show steps towards designing scalable indoor localization systems in a systematic manner that perform effectively across unpredictable environments and are compatible with several emerging technologies. Specifically, we focus on the class of range-based beacon technologies because<br>(1) they can provide accurate ranges given line-of-sight, (2) they can instantly determine a location without requiring devices to move long distances and (3) there<br>are growing standards for range-based technologies such as 802.11mc, BLE5 and ultra-wideband. Unfortunately, installing and mapping beacons is both expensive<br>and time consuming, which continues to hinder adoption. Further, acquiring location from ranges in realistic settings can be inaccurate and slow when a low density of<br>beacons and non-line-of-sight signals are encountered. While having an abundance of beacons increases accuracy and decreases the time to acquire the initial location,<br>it also increases the cost of the system. This thesis aims to lower the barrier to adoption of range-based beacon technologies by reducing the infrastructure required<br>while maintaining high performance in terms of accuracy and time taken to acquire the location and orientation. Our approach leverages additional sources of location<br>information, like geometrical constraints from floor plans to acquire location with a reduced number of beacons, magnetic sensing to rapidly acquire orientation and visual<br>inertial odometry for setup and continuous tracking. We present techniques for location estimation and system provisioning, including beacon placement and map<br>generation, and show how these techniques apply to CPS applications like mobile augmented reality and first-responder localization.