[1] After Semple quit the state printer job in 1874, the family relocated to Vancouver, Washington, across the Columbia River from Portland.

[1] President Grover Cleveland appointed Semple as the Governor of Washington Territory in 1887, where he served for one term until April 1889.

In 1893, he successfully advocated a bill in the Washington State legislature to facilitate a means of financing privately owned canals by allowing them to sell reclaimed tidelands.

With $500,000 of financing, he himself soon attempted such a canal connecting Elliott Bay to Lake Washington by cutting through Seattle's Beacon Hill: a more southerly route than the Lake Washington Ship Canal that was favored by Judge Thomas Burke and others associated with the Great Northern Railway, and which was ultimately built.

The former Elliott Bay tidelands filled in by his attempt at building a canal soon became the basis of Seattle's Industrial District.