Peter Lassen (October 31, 1800 – April 26, 1859), later known in Spanish as Don Pedro Lassen, was a Danish-born Californian ranchero and gold prospector. Born in Denmark, Lassen immigrated at age 30 to Massachusetts, before eventually finally moving to California (then a part of Mexico). In California, Lassen became a Mexican citizen and received the vast Rancho Bosquejo from Governor Manuel Micheltorena. He is best known as the eponym of Lassen County, California, Lassen Peak, and Lassen Volcanic National Park. Early life Peter Lassen was born in Farum, Denmark, and immigrated in 1830 to Boston, Massachusetts. Born to Johanne Sophie Westergaard and Lars Nielsen, Peter was baptized at the age of one week on December 7, 1800. The patronymic surname Larsen, meaning son of Lars, was applied in his naming and was common among Danish farmers at that time. Lassen used several different spellings while living in Denmark and in Copenhagen, sometimes preferring to be called Peter Larsen Farum, after his birthplace. When he was seventeen, Lassen moved to Kalundborg to learn blacksmithing. He apprenticed under his uncle, Christian Nielsen until 1823, when he moved to Copenhagen to work under a master blacksmith named Sigersted. Pioneering California In 1840, he immigrated to California and became a rancher. Peter Lassen traveled from Keyetsville, Missouri, to Westport, Missouri, a "common place of rendezvous for overland parties". The expedition Lassen joined was made up of missionaries and adventurers, some on their way to California; others headed to the Columbia River basin in Oregon. Lassen met the ship Lausanne on the Willamette River in Oregon. He sailed on July 3, 1840, boarding for passage to Bodega Bay, in Sonoma County, California. The travelers were invited to touch land in California at Fort Ross, and stayed on there until they could procure some horses to travel to Sutter's Fort. Lassen arrived at Sutter's Fort in August 1840, with William Wiggins, who had traveled with him from Westport (now Kansas City, Missouri), over land and by sea for nearly fifteen months starting in May 1839. John Sutter happily welcomed the men and traveled with them from his colony, known at the time as New Helvetia (meaning New Switzerland), to Yerba Buena and Alviso, California, in a small sailboat. While it is likely he was working as a blacksmith during his early years in California, Lassen traveled to Santa Cruz in 1841, where he oversaw the