The state-based and federally facilitated health insurance Marketplaces, or exchanges, enrolled more than eight million people during the first open enrollment period, which ended March 31, 2014. There is significant variation in how states have designed and implemented their Marketplaces. We examined how premiums varied with states' involvement in the Marketplaces through governance, plan management authority, and strategy during the first year that the exchanges have been open. State-based Marketplaces using "clearinghouse" plan management models had significantly lower adjusted average premiums for all plans within each metal level compared to state-based Marketplaces using "active purchaser" models and the federally facilitated and partnership Marketplaces. Clearinghouse management models are those in which all health plans that meet published criteria are accepted. Active purchaser models are those in which states negotiate premiums, provider networks, number of plans, and benefits. Our baseline estimates provide valuable benchmarks for evaluating future performance of states' involvement in governance, plan management, and regulatory authority of the insurance Marketplaces.