Just yesterday I was reading Gary Doyle's fantastic biography on Ralph de Palma (Gentleman Champion: Golden Age Books, 2005) and came across a picture (p. 222) that depitcs Johnny Aitken at the Sheepshead Bay Speedway in 1916. The image is credited to be from the William Collins Collection —unfortunately, I haven't been able to find it on the net. What really drew my attention was the panning effect: the car is on focus [sic] while the grandstand at the background is totally panned.
At first I thought that I had never seen this panning effect on such an old picture, but then the image of Jacques-Henri Lartigue taken during the Grand Prix de l'ACF 1913 came to my mind. In any case, this picture has become very popular because it combined the panoramic photographic technique with a focal plane shutter or 'slit-scan' distortion (explained here).
In Lartigue et les autos de course (Motors Mania, 2008), Pierre Darmendrail explains that (...) to create the impression of speed, Lartigue used the panoramic photographic technique, rather uncommon at the time, and which consisted in following the movement of the subject by panning the camera at the same speed. In his diary he notes that the idea had first occured during the 1912 ACF Grand Prix to photograph Boillot's Peugeot. It is true that some of the photographs of the race had been taken using this technique, but Lartigue is mistaken as to the time at which the idea crossed his mind as he had already been experimenting with the method for a long time: as early as 1908-1909 there are pictures of model aeroplanes that he and his brother Zissou built, photographed in full flight and obviously using the panoramic technique.
Indeed, Lartigue had first employed this photographic technique —during a motor race— on occasion of the Grand Prix de l'ACF 1912. Page 73 depicts the picture of Georges Boillot —it can be found too in the albums of Lartigue: here (p. 23/144)— where it can be easily observed that the photographer was following the motion of the car with his camera:
It is clear that the 'slit-scan' distortion was very common at the time because of the use of cameras with a focal plane vertical shutter. As an example, this page from La Vie au Grand Air no. 460 (13 July 1907), where funnily all pictures had been taken statically —note the frozen background— with a shutter speed of 1/2000 sec: