During the 1920s, the volcanic activity at Lassen Peak had greatly diminished. However, that did not mean that interest lessened. Dr. Thomas A. Jagger, a leading volcanologist of that era, had plans for Lassen. In June 1925, he visited Lassen Park to address a congressional delegation that was on a fact-finding trip. He urged that funding be appropriated so that Lassen Peak could be monitored, as had been done in Hawaii. His request was granted, and in July 1926, he announced the forthcoming establishment of the Lassen Volcanic Observatory by stating, “We intend to have the observatory in operation by September 1. By placing an observatory at Lassen the government indicates the importance of carefully recording all data concerning active volcanoes.” In September the observatory became a reality under the auspices of the United States Geological Survey (USGS) which put R.H. Finch in charge. Seismographic instruments were installed at Manzanita Lake and Mineral. A third machine was placed in the fire lookout on Mount Harkness when the lookout was built in 1930. The USGS closed the observatory operations in 1935.
On a final note Jaggar stated that Lassen Peak’s next eruption would occur on its southwestern flank.