1907 - Arnold Munro is born, the result of his father's experiments on his hidden island lab.
1925 - 18-year-old Arnold leaves the island to explore the world.
1927 - 20-year-old Arnold attends school in America where he earns the nickname 'Iron'.
1930 - 23-year-old Iron graduates with a double major after only three years.
1932 - 25-year-old Iron earns a masters degree in physics.
1934 - 27-year-old Iron earns a doctorate in atomic energy.
1936 - 29-year-old Iron earns a second doctorate in quantum mechanics.
1938 - 31-year-old Iron begins working against the Nazis attempt to steal or control his work.
1945 - 38-year-old Iron & Sandra Knight are flung into the timestream in the temporal explosion that killed the rest of the Freedom Fighters.
57 years ago - 38-year-old Iron reappears, and stays with Sandra Knight while they attempt to rebuild their lives.
55 years ago - 40-year-old Iron returns to his father's island and begins rebuilding it after Sandra Knight leaves him.
49 years ago - 46-year-old Iron, with his labs rebuilt, begins his research again. He occasionally works as a consultant to world governments.
38 years ago - 57-year-old Iron assists the All-Star Squadron, but declines their offer of membership.
27 years ago - 68-year-old Iron's adventures are published as popular novels, which inspire a young Clark Kent.
23 years ago - 72-year-old Iron consults with Checkmate, where he finally reconnects with Sandra Knight.
16 years ago - 79-year-old Iron consults with Michael Holt on the construction of the Justice League satellite.
14 years ago - 81-year-old Iron joins Amanda Waller's Freedom Fighters, specifically to look out for Sandra Knight's interests in Checkmate after she is forced into retirement.
6 years ago - 89-year-old Iron helps Sandra Knight oust Amanda Waller as the head of Checkmate and promote Mr. Bones in her place.
"Arn" Munro was a minor character from Steel & Street comics in the 40's, loosely based on a series of short stories by John W. Campbell. In the mid-eighties, after the Crisis of Infinite Earths removed Superman from the Golden Age, there were several stories that needed a character LIKE Superman in order for all the still-in-continuity stories featuring the characters to make sense. This was a fairly regular practice at the time, and the result in this case was Iron Munro.
The exceptionally cool thing about Iron was his clear influence by Pulp adventure character Doc Savage. He was a scientist born in his father's lab, gifted with exceptional biology and a long life. We've also taken a lot of influence from a similar character, Alan Moore's Tom Strong. We've given him a cool island laboratory, and stretched his influence all across the timeline, making him integral in the construction of the facilities for the All-Star Squadron, the Justice League, and Checkmate.
As Iron Munro is meant to be a personal hero to Superman, it's quite easy to introduce the idea that young Clark read Iron's serialized adventures, especially since Iron is actually based on characters from pulp serials. Also, Iron's decades-long relationship with Sandra Knight is a huge part of his character, and it gives us their awesome Granddaughter, Kate Spencer.
Ultimately, Iron is a cool background character running through almost all of DC's history, and including him in our timeline just adds one more awesome element to our continuity.