Vintage cars are not valued by Kelley Blue Book. According to Cars Direct, this classification of older cars is reserved for vehicles manufactured from 1919 to 1930. Kelley Blue Book lists values for vehicles over 21 years old, starting with the 1946 model year, in its Early Model Car Guide.
The Early Model Car Guide is referred to on Kelley Blue Book's frequently-asked-question webpage, which goes on to state that the guide is available in print for purchase as an annual subscription or on a single book basis. The company does provide values for classic cars and antique cars. According to Cars Direct, classic cars are vehicles over 40 years old and manufactured after 1925, while antique cars are over 45 years old that have no modifications.