MANY years ago, at least for daylight operations, the length of the runway was easy to determine as you approached the threshold.
Instead of what the europeans call piano keys at the threshold, there were tally marks, each mark one thousand feet of runway, and the strike mark meant five thousand feet of runway
look at very old pictures of runways, I mean circa 1950s or so and you will see them.
llll / I wish I could get the / on top of the llll to indicate five.