The Lewis and Clark expedition was only the second 'official' transcontinental crossing of North America north of Mexico by a person not of the indigenous peoples of the Americas, having been preceded to the Pacific coast (on July 20, 1793) by a Canadian expedition led by explorer Sir Alexander Mackenzie. Mackenzie had previously crossed North America in 1789 as well, but had turned north at the Continental Divide, also becoming the first European to reach the western Arctic Ocean.