Interpreting boxplot VS stacked histogram in example

Question

I understand what a boxplot and histogram are supposed to show, but I'm a bit confused on how it is being presented in this graphic printout from R. The picture is taken from Beyond Multiple Linear Regression by Roback and Legler.

The response variable under study is horse's speed. In the exploratory part of this activity we have the following set of plots. The ones circled I'm having trouble interpreting. Year as a variable is self explanatory, the condition variable is a categorical variable with three levels. The data is the speed of the winning horse of the Kentucky derby for each year.

In looking at the boxplot the $X$ - axis is the year and the $Y$ - axis is the track condition. Implicitly I do get that the boxplot is showing the median speed at each track condition, but that is not being conveyed in terms of the labelling. When looking at the labelling I would gather that the "median" year is what is being captured by the boxplot. But that doesn't make much sense in this context. Am I missing something in what I'm looking at? because I don't see how you can have median year for an event having one occurrence each year.

The graphic I'm discussing:

Answer 1

When looking at the labelling I would gather that the "median" year is what is being captured by the boxplot.

That's correct, that's what is being displayed by the median line -- but not only the median, since the boxplot includes other information.

But that doesn't make much sense in this context.

When you plot all variables against all other variables, certainly some of those plots may not make much sense. However, the fact that the typical year seems to change with condition does tell you something; this is quite clear in the histograms. We see that the first condition is relatively more common recently than it was, by contrast with the other two conditions, which mostly appear in the earlier years. The median year by condition tells you something of this same effect.