The Cheetah project is a collaboration with Professor Sangbae Kim to develop a quadruped robot with the speed, efficiency, and agility of a cheetah. The efficiency or cost-of-transport of current legged systems greatly lags biological systems by at least an order of magnitude. The first generation cheetah robot now rivals biological systems with a cost-of-transport of 0.51, unprecedented for robotic legged systems. The key to this advancement has been clever mechanical design coupled with new electrical motors having optimal torque density. The second generation cheetah robot is a work in progress to improve speed and agility. Lincoln Laboratory will contribute high-level route planning and obstacle avoidance algorithms, a new processing architecture, and novel sensor systems while campus works to improve the low-level control of the cheetah actuators to enable new high speed gaits.