As I've been stating, a major factor in the rise of General Motors during the 1920s was Alfred P. Sloan's establishment of a price-prestige hierarchy for GM's various brands. Over the 50 years from 1941 to 1991, when the Saturn brand appeared, the hierarchy, from low to high, was Chevrolet, Pontiac, Oldsmobile, Buick and Cadillac. But during the late 1920s so-called "companion" brands were introduced to fill what seemed to be price gaps in GM's line. In 1930 the hierarchy was approximately (there was price overlapping in a number of cases): Chevrolet, Pontiac, Marquette, Oldsmobile, Oakland, Viking, Buick, LaSalle, and Cadillac.
Cadillac's companion brand was LaSalle, introduced for the 1927 model year. Next to Pontiac, a companion brand that usurped its host brand (Oakland), LaSalle was the most successful companion, lasting through the 1940 model year (though it came close to being ditched in 1934).
LaSalle was highly significant in terms of styling history because it was Harley Earl's first production design for General Motors, a sales success that led to him being appointed head of styling and creating the first American automobile company styling department.
Other comparisons in this series tend to focus on 1929 and 1930, the model years when GM's companion project was at its height. For that reason, LaSalles and Cadillacs are compared using 1929 examples and differences in styling are noted.