Beardsley is a really interesting guy, different from most elite runners. He ran just an awful lot of marathons, close together, during his peak, with several seriously world-contending times in a short span. And his training wasn't the highly technical scientific approach that's come to dominate the big American programs. Still on America's top ten fastest marathoners, 25 years later.
The 13 consecutive PRs is really hard to fathom given that he was in many of those races to win them - meaning he wasn't holding himself back for the purpose of maintaining a streak of PRs. His first two marathons were the only ones in that streak that he wasn't contending for the podium.
He's also inspirational for us masters runners because despite having once been the second-fastest American ever, he continues to run and to have a good time running "slow" marathons - he was still running sub-3 marathons just a few years ago. Most of the elites burn out and stop running marathons, but he's continued, running something 100 now.