Bloomberg Philanthropies launched What Works Cities (WWC) in 2015 to help cities better leverage data and evidence to drive decision-making and improve residents' lives. Over three years, WWC will work with 100 American cities with populations between 100,000 and 1,000,000 to measure their state of practice and provide targeted technical assistance. This paper uses the data obtained through the WWC discovery process to understand how 67 cities are currently using data to deliver city services. Our analysis confirms that while cities possess a strong desire to use data and evidence, government leaders are constrained in their ability to apply these practices. We find that a city's stated commitment to using data is the strongest predictor of overall performance and that strong practice in almost any one specific technical area of using data to inform decisions is an indicator of strong practices in other areas. The exception is open data; we find larger cities are more adept at adopting open data policies and programs, independent of their performance using data overall. This paper seeks to develop a deeper understanding of the issues underlying these findings and to continue the conversation on how to best support cities' efforts in this work.