Why do we celebrate Presidents' Day?

"The United States may be a relatively young country, but in just over 240 years of independence, the United States has had more than 40 presidents. Being president isn't an easy job, so every year we take a day to celebrate and honor the presidents of past and present. This . . . book teaches readers more about the history of the role of president of the United States and highlights . . . influential presidents of the past. Colorful images help readers explore how different families like to celebrate Presidents' Day"--Amazon.