California State Route 161 is a nineteen mile State Highway aligned along State Line Road between US Route 97 and California State Route 139 in Siskiyou County. California State Route 161 bisects what remains of Lower Klamath Lake and is one of the easier ways to access Lava Beds National Monument. What became CA 161 was largely developed as State Line Highway between US Route 97 and Malone Road as part of a 15.4 mile Federal Aid Secondary Program during 1948. The Remaining 3.8 miles of State Line Highway east to California State Route 139 were completed during 1956. State Line Highway was modernized to Division of Highways Standards during 1958 and was assumed under State control as a second segment of Legislative Route Number 210 during November 1959. During the 1964 California State Highway Renumbering the second segment of Legislative Route Number 210 was renumbered to California State Route 161.
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