Across New England, a new model of regional collaboration is increasingly being used by land conservation trusts, watershed associations, state agencies and others. Regional conservation partnerships (RCPs) serve multiple purposes, such as coordinating among the various active groups in the region and allowing them to leverage funding and staff capacity. However, their essential missions are the same--protect more land from development. We use interviews, geographic information systems (GIS), and statistical analysis on 20 case studies to document RCP growth and characteristics and to analyze which attributes most contribute to their ability to conserve land. Along with well-known factors of organizational development, we find that the RCPs that match the size of the partnership region with the territory and capacity of the host partner organization are better able to achieve measurable conservation gains.