288 DAYSSan Francisco · 1915
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The Aeroscope

Joseph B. Strauss's counterweighted steel arm that lifted a two-story cab of 120 passengers in a slow spiral to 265 feet above the Zone.

The Aeroscope, from the album of Exposition president Charles C. Moore
The Aeroscope, from the album of Exposition president Charles C. Moore1915, public domain

Todd compared the Aeroscope to Paris's Eiffel Tower and Chicago's Ferris Wheel. It was the invention of J. B. Strauss of Chicago, head of the Strauss Bascule Bridge Company, and in effect it was one leaf of a bascule bridge stood on end. A steel arm reached 200 feet beyond its pivots and carried a two-story cab for 120 people. Behind the pivots a shorter arm ended in a 380-ton counterweight of steel and concrete. The pivots sat on a steel tower 48 feet high. The tower's round base rode on railway trucks around a circular track 60 feet across.

A clever trick kept the arm balanced. Water tanks under the cab let out each boarding passenger's exact weight in water and pumped it back when he stepped off. Balanced that way, the arm needed little power to rise. Once the cab cleared the neighboring tall structures, gears began turning the whole tower, so the cab climbed in a great spiral and faced every point of the compass. At the top riders were 265 feet above the ground and, because the site itself stood about 65 feet up, some 330 feet above the sea. From there they could see into seven counties and far out over the Pacific. A trip took about ten minutes. Aeroplane propeller blades on the cab's sides steadied it. Todd thought they also helped the picture.

Erection began on October 25, 1914, and the first run was on February 12, 1915, days before the fair opened. It was a marvel but not a business. It took in over $67,000 and had cost almost that much to build, and Todd blamed a poor location with an inconspicuous approach. Strauss went on to greater fame: he is credited as chief engineer of the Golden Gate Bridge, though Charles Alton Ellis did most of its structural design.

Paris had its Eiffel Tower and Chicago had its Ferris Wheel, but the Zone at San Francisco had something that combined a little of both, and in some ways was more interesting than either.

Frank Morton Todd, The Story of the Exposition, vol. II (1921), p. 151

At a glance

  • Arm projected 200 feet beyond the pivots; 380-ton counterweight; cab held 120 people.
  • Tower 48 feet high on a circular track 60 feet in diameter; whole structure about 700 tons.
  • Maximum height 265 feet above grade; about 330 feet above sea level.
  • Erection began October 25, 1914; first operation February 12, 1915.
  • Receipts over $67,000, roughly equal to its construction cost.
The Aeroscope, postcard
The Aeroscope, postcardUnknown publisher, 1915, public domain

Afterward

Removed with the Zone in 1916; its later fate is not recorded in the sources consulted. The site is Marina District housing between Gough and Franklin Streets.

Sources