  Since the end of Run 1 of the LHC in 2012, the outermost ring has been added
to the CMS Cathode Strip Chambers (CSC) endcap muon detector, and the readout
electronics of the innermost ring of CSCs have been upgraded to accommodate the
larger luminosity and collision energy anticipated in Run 2. A major effort was
required to build, install, and commission these new chambers and electronics.
This talk summarizes the improvements made during this upgrade and presents the
performance of the CSC detector during the early stages of Run 2.
