Fort Armstrong (1816-1836) was located on the present-day Rock Island Arsenal along the Mississippi River in northwest Illinois. During that time, the Army kept daily records of temperature at 7 a.m., 2 p.m., and 9 p.m., as well as remarks above the weather. These are the oldest official weather records I’ve seen for a site in Illinois and date back to July 1820. The museum staff at the Rock Island Arsenal scanned the original images for us. Lauren Graham, University of Illinois Department of Atmospheric Science student, organized the images, developed the webpage, and did additional analysis.
Fort Armstrong Weather Records
Months and quarters for which no data was recorded are omitted from the table.
Fort Armstrong Monthly Averages Compared to Modern Record
| Jan | Feb | Mar | Apr | May | Jun |
| Jul | Aug | Sep | Oct | Nov | Dec |
