Slaves? In Alaska?

While driving up the pass, describing the construction of the White Pass and Yukon Route railway, completed in 1900, a conspiring passenger grudgingly suggested, "I bet they used slaves to build the railroad."

Instead of blatantly calling her an over-exaggerating idiot, I simply explained that there were enough people who came up here to find gold and didn't that they could be put to work on the railway.

I wanted to say:

A. This wasn't 1860

and

B. This railway wasn't transcontinental

They just keep on coming.