Serenity Crack was claimed as one of the first 5.11 climbs in the U.S., when it was freed by Tom Higgins and Chris Jones. Tom Higgins as in LongAgo, who often contributes to our debates here. The route was featured conspicuously in an article in the 1972 (?) American Alpine Journal, promoting clean climbing - an article that included photos. (I don't have a copy, but believe the article was by Royal Robbins [Edit: by Tom Frost], and the photos of the pin scarring at the bottom were by jstan.) Serenity was the poster-climb to show why we needed to do things very differently.
In other words, even though it's not a particularly notable route in and of itself, it has history, and to some extent symbolizes the debate around bolts and climbing styles. No one has yet said why the bolt was placed to begin with, but my guess is that when people started to free the route, especially the first pitch, the existing clean protection (hexes and stoppers) wasn't of much use there. To deter further pin scarring of the soft rock, a bolt was placed at about the point where people would otherwise be reaching for a hammer. Having the bolt there then may have been thought the lesser of evils. There was a school of thought then (DR?) that believed nuts + a minimum of bolts [Edit: and/or fixed pins] was better than nuts + pitons.
Of course, back in the good old days, p'terodactyls still nested on Half Dome, and ate rap bolters. #46 was still in training.
Thanks, Clint. I trawled through the AAC website in an attempt to find the article, overlooking that it was right under my nose!
It is important to note that the article was on page 1 of that year's journal - the American Alpine Club (or at least its editor) showed considerable leadership in pushing the debate. In retrospect perhaps the advocates were leaning on a partly-open door, in that nuts very often were easier and faster to use than pitons, and overall as reliable. Also that nuts had slowly been getting better and more common. Nonetheless it was quite a sea change.
Serenity is really just a microcosm of the larger debate about climbers' impacts on the natural and human environments, both as climbers and simply as humans who are often citizens of developed countries. Also about what impacts are acceptable, and how they can be minimized or mitigated.