We have obtained CCD photometry, in the UBV system, for 23 open clusters in order to explore the star formation history of the Cassiopeia region of the Perseus spiral arm of our Galaxy. Magnitudes and colors of 35,788 stars were measured, making this the most comprehensive, homogeneous single study of open cluster properties in one part of the Galaxy. This paper presents an atlas of open cluster photometry that serves as the database for an investigation of cluster properties such as their ages, distances, reddenings, sizes, and richnesses. This information provides insight into the spatial and temporal formation sequence of the clusters and allows an investigation of the stellar content of the clusters to be undertaken.