Fort Belle Fontaine Cantonment Belle Fontaine | |
 Resort ruins in March 2005 | |
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| Location | Fort Belle Fontaine County Park St. Louis County, Missouri |
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| Coordinates | 38°49′36″N 90°12′59″W / 38.82667°N 90.21639°W |
| Built | August 10, 1805 |
| NRHP reference No. | 16000031[1] |
| Added to NRHP | February 23, 2016 |
Fort Belle Fontaine (formerly known as Cantonment Belle Fontaine) is a former U.S. military base located in St. Louis County, Missouri, across the Mississippi and Missouri rivers from Alton, Illinois. The fort was the first U.S. military installation west of the Mississippi, in the newly acquired Louisiana Territory, and served as a starting point for many expeditions to the American West.