A. Competed to Tiger Hill July 1, 1908 to allow the original main line to be cut.
B. Track connection for the excavation of the first and second Gatun locks.
C. Diversion of the original main line for the construction of the dam at Gatun.  The fill was dumped from a high trestle.
D. During the initial stages of the dam construction the West Diversion Channel was left open.  It was closed April 10, 1910 which began the formation of Gatun Lake.

This is an excellent map showing the area of old Gatun.  The map is from Charles S. Small's book Rails to the Diggings.