Jack McClain crossed the finish line ofthe Columbus Marathon yesterday just as volunteers from the Denison University women’s basketballteam began removing advertising banners tied to the barricades that separate participants fromspectators.The large crowds were long gone — nearly 7½ hours after the 26.2-mile race had begun. Those whoremained likely did not even realize that McClain’s finish was a sight worth seeing, for it is notevery day that one gets to watch someone accomplish what only eight other people in history haveachieved: completing a marathon at age 90 or older.Historical significance was not what struck this observer, however, as McClain passed under theelectronic race clock on Nationwide Boulevard showing his time of 7 hours, 12 minutes, 37 seconds,which was 15 minutes better than he expected and 15 spots ahead of the last finisher. My thoughtswere much less high-minded.First: that my pride of having walked 20 minutes from a Downtown parking lot to the ArenaDistrict was duly destroyed by a 90-year-old, 138-pound wisp of a man.Second: that McClain not only is considerably older than those pony-tailed Denison athletescompleting their volunteer task, but perhaps a decade older than their parents’ parents.Jack McClain, born in Sharon, Pa., in 1921 and now living outside Granville, is agenetically-blessed joy of a person. As is his 87-year-old wife, Jeanne.“Well, of course she is,” the man said of his beloved.This column could stand on its own as a tribute to the power of a well-maintained marriage.Instead, it will stick to the marriage between a man and his mission.McClain does not simply run. What this retired mechanical engineer really does is inspire.“He likes to make people smile as he just goes about his day,” said his grandson, John McClain,who ran the full marathon, then doubled back and caught up with Jack in time to walk the last 11miles with the one who “makes you feel you’ve got a lot to look forward to.”Sincere optimism is an undervalued commodity, often squeezed out of the discussion by wittycynicism and self-righteous reality. Jack McClain does not take the bait of those latter betrayers.He remains upbeat and pleasant even during the cool-down of a seven-hour walk around Columbus.Running does not measure McClain’s worth. Still, it is an impressive component of his lifestory.McClain walks his races now, but it is a fairly recent development. He began the running thingin 1975. McClain was 55, and his first race was the Fourth of July 5-miler in Granville. The firstmarathon came in 1978 in Athens, Ohio, when he averaged 9:34 a mile. He since has participated in45 marathons, including 30 in Columbus, running them until about seven years ago when walking tookover.He has never failed to finish a marathon. According to Running USA, he is the ninth man tofinish a marathon at 90 or older.It likely will not reach 91. McClain concluded after yesterday’s race that, “I think this is mylast.”If yesterday was the finish, McClain will leave a legacy of fashioning a brighter frame of mindamong those who encounter him, which is why he and his family received the Nationwide InsuranceColumbus Marathon Spirit Award this year. He has come through radiation for prostate cancer (1986)and survived a severe head injury in 2002 that required a 17-day stay in intensive care.“The nurses and all my friends thought that the fact I was in good health pulled me through,” hesaid, adding that the reason he still walks 5 miles every weekday is because, “if you arephysically active it’s going to do some good. It certainly has been good for me.”Good for others, too. The aging walker who finished amid a marathon teardown has spent more thana quarter of his life building up those around him. It has been a course well run.Rob Oller is a sports reporter for The Dispatch.