In a previous post I mentioned that the 7th hole has very sandy soil, which isn't all that common for the Chicago area, and I think that the history behind that sandy soil is a unique feature of Calumet Country Club.  Our course sits on the edge, or the beach, of Lake Chicago which was a larger version of Lake Michigan that was created as the glaciers retreated at the end of the last ice age.  There are also some other pockets of sand on the course, but that is the most concentrated area. 

In these soil samples from the 7th hole rough, you can see that once you get about six inches down into the ground, the soil is pure sand.  The top is also very sandy, but has some organic matter mixed in which gives it a darker color. 

The sandy soil is also home to another unique feature of Calumet, black oak trees.  Most of the trees between the 4th and 7th holes are black oak trees, which grow best in sandy soil.  This line of black oak trees is a natural feature and continues into the neighborhood on the other side of Dixie Highway along with the "beach" sand.  When the course was built, these were pretty much the only trees on the course.  In fact, there is a picture in the men's grill taken in that direction from the clubhouse, and those oak trees are the only trees in the picture.