Federally Qualified Health Centers--commonly referred to as Community Health Centers (CHCs)--serve as a safety net for people who did not gain health insurance under the Affordable Care Act (ACA), including those immigrants not eligible for Medicaid or health insurance exchange coverage. ACA-driven changes in health insurance coverage, funding, and related policy have created new challenges for these safety net organizations. This policy brief reports the findings from analyses of the U.S. HRSA Uniform Data System and interviews conducted in 2014-16 with the leadership of 31 CHCs. The CHCs were located in communities with high concentrations of immigrants and uninsured residents, in states that either expanded Medicaid (California and New York) or that chose not to expand it (Georgia and Texas). The study found that most CHCs now see more patients, including significant numbers without insurance. The ACA has brought new resources to CHCs but has also reinforced challenges, including the need for stable revenue streams, sufficient staffing support, and assistance in leveraging new reimbursement mechanisms. Policy recommendations to address these challenges include continuing core federal funding, insuring the remaining uninsured, addressing workforce challenges, and preparing CHCs for alternative payment mechanisms.