1. It is the only series ever officially endorsed by the State of Texas and the Texas Rangers.

Eat your heart out, Chuck Norris. Wait, sorry, we take that back. You don't want to upset Chuck.

2. It was a spin-off of a series that also spawned 'The Rifleman.'

Culp's character originally appeared on an episode of Dick Powell's Zane Grey Theatre, "Badge of Honor." The anthology series was a breeding ground for iconic television Westerns. The Rifleman, Johnny Ringo, The Westerner and Black Saddle all stemmed from Zane Grey Theatre. Additionally, The Rifleman spawned Law of the Plainsman. It's a big family tree, including Trackdown's own popular spin-off…

Image: The Everett Collection

3. 'Wanted: Dead or Alive' is a spin-off of 'Trackdown.'

Steve McQueen's bounty hunter character Josh Randall first appeared on Trackdown, in the late season one episode appropriately titled "The Bounty Hunter."

4. Robert Culp suggested casting Steve McQueen, who played three roles on the series.

Culp and McQueen were buddies long before the show. Their friendship traced back to their time as "struggling actors living in Greenwich Village riding their motorcycles around town," according to the biography Steve McQueen by Marc Eliot. Culp pushed Dick Powell to bring in the man's man, who also played twin brothers in the episode "The Brothers."

5. Episodes were based on true case histories of the Texas Rangers.

Yep, it's nearly a reality series, as plots were "ripped from the pages" of true Texas Rangers cases from the 19th century. The series proudly touted this fact after the closing credits. 

6. Even prisoners were big fans of the show.

The Texas Prison Rodeo was an annual event held for prisoners in the Texas penal system. Perhaps you remember it from the movie Urban Cowboy. Robert Culp made appearances at the Texas Prison Rodeo, and the fictional Ranger was warmly greeted. Convicts named Culp the honorary president of the "Crime Doesn't Pay Club." As told in the book Convict Cowboys: The Untold History of the Texas Prison Rodeo, prisoner Bill Weems, the actual president of the club, presented the actor with an award scroll. In addition, a group of cons wrote and sang Culp a song called "Trackdown Ballad."

7. Robert Culp wrote one episode.

He penned the season two tale "Back to Crawford," which featured his then wife Nancy Asch-Culp. That's her on the left.

Image: The Everett Collection

8. Culp was offered the lead in 'Man from U.N.C.L.E.'

The actor turned down the chance to portray Napoleon Solo, saying he found the script "cheesy," according to the book Cosby: His Life and Times. Instead, Culp wrote his own spy series script, with the guidance of one-time Trackdown scribe Sam Peckinpah, a more serious and hard-boiled secret agent series that became I Spy.

Image: The Everett Collection