Did Bayou St. John at one time run all the way to downtown?
Yes. Maps show Bayou St. John extended into areas much closer to the French Quarter, but we have to go way back to explain. Shortly after the last ice age ended, glaciers began to melt and the seas began to rise again. About 4,000 B.C. the shoreline stabilized along the Gulf much as it is today, except for Louisiana. Its shoreline is believed to have been about where the Northshore of Lake Pontchartrain is today.
The Mississippi River continued to build deltas in the area, creating a bay about 2,000 years ago that we now know as Lake Pontchartrain. The lower Mississippi had changed course several times — and still continues to try. Until we built levees, the river overflowed its banks annually, and this water seeking the Gulf carved out bayou tributaries.
It is believed this process created Bayous Metairie and Gentilly flowing between the Mississippi River and Lake Pontchartrain. Bayou St. John, once known as Bayou Choupic by the Acolapissa Indians, originally formed about 500 years ago as a tributary of Bayous Metairie and Gentilly.
Jean-Baptiste Le Moyne de Bienville and his brother Pierre Le Moyne d'Iberville explored the lower Mississippi River in 1699. During this trip, they were shown the river terminus of a portage (the way to go from one body of water to another) that led to Bayou Choupic (St. John). It was on March 9 that Iberville wrote, "The Indian who accompanied me revealed a terminus of the portage from the southern shore of the bay where the Indian boats land in order to descend this river. They drag their boats along a fine path ..."
This portage eventually led to the decision to develop a city at the site of present-day New Orleans, and the "fine path" later became Bayou Road, the oldest road in New Orleans.