美國聯邦公路管理局在1955年9月15日批准將舊金山灣區郊區的公路納入州際公路系統,包括隨後被編號為280和680的外環道路。680號州際公路為東半環,南起聖荷西市區的101號美國國道,沿尼米茲高速公路(當時的17号加利福尼亚州州道/69号加利福尼亚州州道,目前的880號州際公路)至溫泉鎮分出(目前262号加利福尼亚州州道的所在位置),接上21号加利福尼亚州州道至貝尼夏,再轉向西北至瓦列霍匯入80號州際公路[14][15]。第一段修築的公路是在1950年代晚期完工的從核桃溪的North Main Street至快樂丘的Monument Boulevard(與24号加利福尼亚州州道共構)[16][17]。1960年3月22日,核桃溪外環道路至South Main Street通車,此路段可接往奧克蘭方向的24号加利福尼亚州州道[18]。其後十年,由瓦列霍至聖荷西傳道區與238号加利福尼亚州州道交會點陸續分段通車,僅存的21号加利福尼亚州州道自貝尼夏至柯蒂里亞路段亦升級至州際公路標準[19][20]。
^"An act...relating to...the addition of certain highways to the State system.", 1933 chapter 767, p. 2036: "State Highway Route 75 near Walnut Creek to State Highway Route 5 near Stockton via Antioch." "State Highway Route 75 near Walnut Creek to Livermore-San Jose Mission Road near Scotts Corners." "State Highway Route 5 near Mission San Jose to State Highway Route 5 near Livermore."
^"An act to establish a Streets and Highways Code...", 1935 chapter 29, p. 281, 283: "Route 75 is from: (a) Oakland to Route 5 near Stockton via Walnut Creek and Antioch..." "Route 107 is from: (a) Route 75 near Walnut Creek to Route 108 near Scotts Corners..." "Route 108 is from Route 5 near Mission San Jose to Route 5 near Livermore."
^"An act...relating to State highways.", 1935 chapter 274, p. 959, 281: "Route 74 is from a point on Route 8 near the Napa Y to Cordelia via Vallejo and Benicia."
^"An act...relating to state highway routes.", 1949 chapter 1467, p. 2555: "Route 75 is from:...(b) Route (a) above, north of Walnut Creek to Martinez..."
^State Set to Take Over Benicia Ferry. 聖馬刁時報. 1953年9月29日.
^"An act to amend...the Streets and Highways Code, relating to state highways.", 1976 chapter 1354, p. 6176, 6178: "Route 680 is from: (a) Route 101 near San Jose to Route 780 at Benicia passing near Warm Springs, Mission San Jose, Scotts Corners, and Sunol, and via Walnut Creek. (b) Route 780 at Benicia to Route 80 near Cordelia." "Route 780 is from Route 680 at Benicia to Route 80 in Vallejo."