Most Boulder County residents were born in the United States; as we see in Figure 1, mostly in the states directly northwest of Colorado.
Figure 1. Birthplaces of native-born Boulder County residents, 1920, excluding Colorado. (Hover over to see counts per country.)
However, about 13 percent of Boulder County residents were born overseas; mostly in Europe, but also in Canada, Mexico, and Japan.
Figure 2. Birthplaces of foreign-born Boulder County residents, 1920. (Hover over to see counts per country.)
