On May 1, 1837, the Skrang Ibans invaded the Jagoi-Bratak Bidayuh settlement on top of Bratak Peak, killing over 2,000 Jagoi-Bratak Bidayuh men and taking 1,000 women captive. Panglima Kulow, head of Jagoi-Bratak Bidayuh community, and a handful of his followers survived the massacre. In 1841 Sir James Brooke, who was then the newly installed White Rajah of Sarawak, was able to rescue some of the women taken captives. Each year on May 1, descendants of the survivors of the 1837 massacre hold Jagoi-Bratak Day on top of Bratak Peak in Bau in memory of their ancestors. A memorial stone was erected on May 1, 1988, to mark the day.
Gold began being mined in Bau in the 1840s. It was discovered by Chinese miners from Pangkalan Tebang. After the Chinese uprising in 1857, the mining operations were gradually taken over by The Borneo Company with the last Chinese syndicate being bought out in 1884. In 1898, The Borneo Company introduced the cyanide process for extracting the gold, which led to increased environmental pollution. The mines were closed in 1921 because most of the easily reachable minerals had been removed. But during the Great Depression Chinese miners continued to work the mines. The mines were reopened in the late 1970s when world gold prices soared, but closed again in 1997 when the Asian financial crisis started. However by 2002, Preston Resources began developing the mining operations formerly held by Malaysia's Oriental Peninsula Gold. In 2006, Zedex Minerals purchased the controlling interest.