Complex sentence: Welsh pioneers were the first to settle in the Malad Valley in the 1860s, which is one of the reasons that Malad Valley has the largest per capita concentration of people of Welsh ancestry outside the country of Wales itself.
Split into simpler sentences: Welsh pioneers were the first to settle in the Malad Valley in the 1860s. Whish is one of the reasons that Malad Valley has the largest per capita concentration of people of Welsh ancestry outside the country of Wales itself.