In 1857, British Royal Engineers established their Camp Semiahmoo which was later used as a base to survey the international border. Soldiers described the Semiahmoo as "harmless and peaceable." By the 1860s, Roman Catholic missionaries had a successful church among the Semiahmoo and a gold rush poured settlers and miners into the area. A new trail was built to link Semiahmoo Bay with Fort Langley. The 1862 Pacific Northwest smallpox epidemic and another epidemic in 1888 resulted in heavy loss of life among the Semiahmoo. Many Semiahmoo worked as loggers or charged tolls for transportation of logs across their land. Reef-netting also became commercialized until a continuous line of traps by Alaska Packers ended their industry in 1892.
