The town of Pemberon is located at the north end of Lillooet Lake. According to BCGNIS, Pemberton was originally referred to as Port Pemberton, named after Surveyor-General
Pemberton.1
In this despatch, Douglas states that the only route into Pemberton was a 34 mile horse-way from Anderson Lake that was built in 1858.
1. Pemberton,BC Geographical Names Information System.