A large literature on teacher collective bargaining describes the potential influence of provisions in teacher union contracts, but little is known about the determinants of these provisions. Using a unique dataset of every active teacher collective bargaining agreement in Washington state, we find that the proximity of two districts is a significant predictor of the similarity between the districts' CBAs. This suggests that spatial relationships play a major role in determining the provisions that appear in a district's CBA. These spatial relationships are more pronounced for different subsets of provisions, including a subset of high-profile provisions and provisions dealing with Association rights, benefits and leave procedures, hiring and transfer policies, and teacher workload agreements. Our findings suggest that policy makers seeking to understand the determinants of teacher collective bargaining provisions must consider the role that spatial relationships play in the process. (Contains 6 tables and 29 footnotes.)