Cathode strip chambers for the CMS endcap muon system

In the CMS detector, the endcap muon system covers a large rapidity interval and has capability to trigger on muons down to very low transverse momenta for B physics. Cathode Strip Chambers (CSCs) have been chosen as the active detectors for this system, due to high rate and precision capabilities. The CMS endcap muon system is by far the largest deployment of CSC chambers and electronics so far envisioned. We describe the LHC environment and requirements for this system, the status of the design and prototyping of the CSC muon detectors, and the electronics required for readout and triggering. Of particular relevance for B physics is the planned capability to trigger on muons down to the momentum limits imposed by their ranges in steel. In the endcap system this corresponds to a very low PT.