I had long assumed, in the absence of any evidence to the contrary, that “Road Racing at Home and Abroad in 1908” by C.G. “Chris” Sinsabaugh was the first of its type. Appearing in the 7 January 1909 issue of Motor Age (Volume 15, No. 1), the article covered American and European road racing for the 1908 season (28-33). It also covered the following American contests of 1908: reliability runs (34-36); hill climbs (37); “Other branches of motoring sport” — with track racing being notably absent, (38-40); and, “Support given competitions by makers” (40-41).
However, a week prior to the Sinsabaugh review it seems that The Motor World published its “Review of the Year in Racing” for the 1908 season. Appearing in the 31 December 1908 (Volume 19, No. 14) issue of the automotive journal, unlike the review in Motor Age, this review does not carry a byline. Also, as with Sinsabaugh, Its coverage tends to focus on road racing, although The Motor World review devotes some attention to the war between the A.A.A. and the A.C.A., a topic that Sinsabaugh generally omits from his survey of the 1908 season.
Searches of earlier volumes of The Motor World as well as other contemporary American automotive journals have failed to discover an earlier review devoted exclusively to motor sport. There might be an earlier seasonal review of automotive contests lurking somewhere out there, but thanks to gaps in the archival material or simply overlooking it, I have yet to find it.