As often happens, I find an intriguing map at the Missouri History Museum’s website and it leads me down a rabbit hole. In this case, it was the plat map above, of the Marais Castor Addition or Subdivision from 1853. Marais Castor means “Beaver Marsh” in sort of a mix of Latin and French, and yes, you might be thinking, isn’t there a constellation named Castor and Pollux? Yes, the Gemini Twins were important in Greek and Roman mythology. But I digress. Marais Castor was also the name of the estate of William Clark out in St. Louis County, but it is long gone.

There was an auction for the land owned by Charles Semple in 1853, and you can see that auction map above. Below, in Compton and Dry from 1876, we can see that twenty years later that little development outside of agricultural uses had occurred in the addition. This is extremely common; from my experience examining plat maps filed in the Recorder of Deeds, most land was platted and subdivided by the 1870s, even if it took far longer to be developed.

So why did Semple name the subdivision Marais Castor? Well, there was/is a creek with that name that flows to the south in the Wells-Goodfellow neighborhood, which you can see on this topographical map. And it all makes sense now why MSD has been building retention basins in this area–it is to deal with the flooding from the former creek!