Patrick indicated that Mound 85 was oval in outline with an orientation of the long axis about east-northeast to west-southwest. Using the scale on the Patrick map gives about 225 feet (68.6 meters) for the length and about 100 feet (30.5 meters) for the width. There is no indication of height for this mound.
Other early maps also show a mound in this location. The McAdams (1882) Map shows an outline and orientation very similar to the Patrick Map. The Cyrus Thomas map of 1894 shows Mound 85 with an oval outline but an east-west orientation. Both McAdams and Thomas indicate the height was about 10 feet (3.05 meters). The Peterson-McAdams Map of 1906 shows only three mounds in the Powell group. The northernmost mound, which may be Mound 85, is assigned a height of only 5 feet (1.5 meters). This mound does not appear on Moorehead’s maps until 1929. However, he does not give any indication of its dimensions. It is represented as slightly ovoid. The USGS 1931 compilation map has Mound 85 shown clearly by two contour lines. This suggests that in the late 1920s Mound 85 was at least 10 feet (3.05 meters) high. The orientation at that time was northeast to southwest. The difference between the earlier heights and orientations and the later ones may be due to cultivation of the area.
No excavations are reported for this mound. The data presented by Titterington (1938: 15) as coming from Mound 85 are actually from Mound 84. Bareis states: “The last attention paid to any of the… [Powell Mound Group] occurred in 1960 when a building stage of Mound 85 was exposed by heavy equipment in conjunction with the construction of Federal Aid Interstate Highway 70” (Bareis 1960: 15).
The location of Mound 85 was determined by plotting coordinates derived from the Patrick Map on the 1966 UWM Map. A slight rise in elevation is all that can be seen today. This is the small remnant of this once massive mound.
In summary, Mound 85 was a large mound approximately 70 by 30 meters (250 by 98 feet) and over 3 meters (9.8 feet) in height at the western limits of the Cahokia site on the banks of Cahokia Creek. It had an oval base with the long axis oriented several degrees off an east-west line. It was plowed down over the period from the 1870s to the mid 1900s. It was finally destroyed in 1960 during construction of Interstate 70. Mound 85 was probably a ridged mound rather than a platform.