The Urban Institute's Health Reform Monitoring Survey (HRMS) has been tracking insurance coverage since the first quarter of 2013. Today, we report the first estimate of how the uninsurance rate has changed through early March 2014. These results track changes through most of the first Affordable Care Act's (ACA) open-enrollment period, which ended on March 31, 2014. Analysis of data from the March 2014 HRMS shows the uninsurance rate for nonelderly adults (age 1864) was 15.2 percent for the nation, a drop of 2.7 percentage points since September 2013, the month before ACA open enrollment began. This represents a gain in coverage for about 5.4 million adults.