Mount Lassen By facebooker_10215913112251274 1821 Jedediah Smith, first white man to reach the Lassen Peak area 1830 Peter Lassen leads immigrants past the peak to the Sacramento valley; Lassen Peak is later named after him 1851 Grover Godfrey; first recorded ascent of Lassen Peak 1864 Helen Tanner Brodt; first women to reach the top of the mountain 1907 Theodore Roosevelt establishes the Lassen National Monument May 22, 1915 Mount Lassen powerful eruption 1916 Monument expanded to establish the Lassen National Volcanic Park 1950 Naturalist Paul Schulz documents 30 steam vents at the summit of Lassen Peak 1976 13 seismometers placed to monitor continuing volcanic activity Jul 9, 2009 Summit Trail closed after tragic accident 2015 Summit Trail reopens