The Massachusetts Library Network Consortium (MassLNC) has been collaborating for the past two years to implement the open source integrated library system Evergreen for its member libraries. Three library networks - CW MARS, MVLC, and NOBLE - received grant funding to investigate and select a single ILS and develop it to better meet local needs. MVLC transitioned to Evergreen in 2011, and CW MARS and NOBLE were set to go live in May 2012. Through shared decision making and a mutual support structure, the networks have undertaken development projects like cataloging enhancements and have benefited from involvement in the broader Evergreen community. While the transition presented challenges like a changing public catalog, the switch to open source offers libraries more