A CMS Level-1 Track Finder for the HL-LHC

<!--HTML-->The High-Luminosity LHC will put significant demands on trigger systems. To control trigger thresholds, the CMS Collaboration is designing a novel Level-1 track trigger. The Outer Tracker will use modules with pairs of sensor layers to read out hits compatible with charged particles above 2-3 GeV. The system will combine these front-end trigger primitives to reconstruct tracks, providing a measurement of P_T, \eta , \phi, and z_0. This presentation will introduce the CMS L1 track finding system: the algorithm and its estimated performance, hardware prototypes, and the unique challenges associated with this system.