The first and foremost was the Ohio River, which flowed into the Mississippi River.

"Results": [
    {
        "TypeName": "LOC",
        "Text": "Ohio River",
        "Start": 31,
        "End": 41
    },
    {
        "TypeName": "LOC",
        "Text": "Mississippi River",
        "Start": 65,
        "End": 82
    }
]