With the football season underway, lots of sports fans are thinking about the National Football League (NFL).

I have been thinking about the NFL for more than five years. That’s because my latest book — “Gridiron: Stories From 100 Years of the National Football League” — has just been published.

A book such as “Gridiron” — 100 pages and almost 70 illustrations by artist James Ransome — doesn’t just appear on the bookshelves. It’s a lot of work.

I read more than 40 books and dozens of articles to collect the stories in the book. Those stories include how the NFL started in an automobile showroom in Canton, Ohio, in 1920. Another is about how the first championship game was played in a Chicago ice rink. And another is about how only 31 of the 81 players selected in the first NFL draft ever played in the NFL.

Still, with all the stories in the book, there are plenty of entries from my 500-plus pages of notes that I couldn’t fit into the 20 chapters of “Gridiron.” Here are some of the stories I had to leave out:

● Early NFL games were generally low scoring. The Hammond Pros did not score a single point during the 1922 NFL season. (They played only six games.)

● The Duluth Eskimos played all but one of their 23 games on the road during the 1926 and 1927 seasons. The team folded after the 1927 season.

● The first night game in NFL history was played on November 6, 1929, between the Providence Steam Roller and the Chicago Cardinals. The ball was painted white so the players could see it more easily.

● The first broadcast of an NFL game on television occurred October 22, 1939, when the Philadelphia Eagles played the Brooklyn Dodgers at Ebbets Field in Brooklyn, New York. Not many people watched the game. Only about 1,000 New York City residents owned televisions at the time.

● Byron “Whizzer” White led the NFL in rushing yards during the 1938 and 1940 seasons. White did not play in 1939 because he was attending Yale Law School. White later served as a United States Supreme Court justice from 1962 to 1993.

● Helmets were not required equipment in the NFL until 1943. Ouch!

● Running back Jim Brown led the NFL in rushing eight of the nine seasons he played (1957 to 1965). Brown was also an all-American in lacrosse at Syracuse University. He is a member of the Pro Football and National Lacrosse halls of fame.

● You may have heard the term “taxi squad.” Those are extra players a team keeps around who are not on the official roster. The term started with Paul Brown, who was the Cleveland Browns’ head coach from 1946 to 1962. Brown would obtain jobs with Cleveland taxi companies for his extra players.

I think kids ages 8 to 12 and their parents will enjoy the stories in “Gridiron.” I know I had fun researching and writing it.