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KIC8462852 is a completely-ordinary F3 main sequence star, except that thelight curve from Kepler shows episodes of unique and inexplicable day-long dipswith up to 20% dimming. Here, I provide a light curve of 1338 Johnson B-bandmagnitudes from 1890 to 1989 taken from archival photographic plates atHarvard. KIC8462852 displays a secular dimming at an average rate of0.164+-0.013 magnitudes per century. From the early-1890s to the late-1980s,KIC8462852 faded by 0.193+-0.030 mag. The decline is not an artifact becausenearby check stars have closely flat light curves. This century-long dimming isunprecedented for any F-type main sequence star. Thus the Harvard light curveprovides the first confirmation (past the several dips seen in the Kepler lightcurve alone) that KIC8462852 has anything unusual. The century-long dimming andthe day-long dips are both just extreme ends of a spectrum of timescales forunique dimming events. By Ockham's Razor, two such unique and similar effectsare very likely produced by one physical mechanism. This one mechanism does notappear as any isolated catastrophic event in the last century, but rather mustbe some ongoing process with continuous effects. Within the context ofdust-occultation models, the century-long dimming trend requires 10^4 to 10^7times as much dust as for the deepest Kepler dip. Within the context of thecomet-family idea, the century-long dimming trend requires an estimated 648,000giant comets (each with 200 km diameter) all orchestrated to pass in front ofthe star within the last century.

KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989