If your 1¢ stamp appears like this, with a cross gutter between sheet of 25 stamps, you have #766

If your 1¢ stamp appears like this, with a cross gutter between the stamps, you have #766a

If your 1¢ stamp appears like this, with an adjacent gutter on any of the sides, you have #766a

Fort Dearborn was a wooden stockade built in 1803 on the south bank of the Chicago River as the U.S. Army’s westernmost outpost . It was located near the mouth of the river, at the intersection of what is today, Michigan Avenue and Wacker Drive. In the war of 1812 it was burnt to the ground by the Potawatomi Native Americans. it was rebuilt in 1816 and de-commisioned in 1840, it then served as the harbor masters office until its demise in 1857 (see below).

A replica of Fort Dearborn was set up at the Chicago Century of Progress International Exposition but it was not a faithful replica.The top image is the blockhouse of Fort Dearborn in 1853, The second image is a photo of Fort Dearborn taken three years later. Another year later, in 1857 it was destroyed by fire with the blockhouse surviving until another fire destroyed it in 1871. The bottom image is a photo of a replica of the Fort at the 1933 Chicago Expo.