It was the era when pioneers and mountain men, primarily of European descent, traveled west across North America to explore and settle the lands west of the Rocky Mountains and north of California. Some also arrived via the Pacific Ocean, traveling by ship either around Cape Horn or by changing ships at Panama. The period begins after the explorations of the lower Columbia River by Robert Gray and George Vancouver in 1792, along with the 1804–1806 Lewis and Clark Expedition to Oregon Country, and runs until circa 1890 when railroads and urban centers created a more settled state.