Format 1
Used from 1927 to 1933. Main features: "THE HARDY BOYS," in an italic serif font, is centered, with a thin line directly beneath. The book's title is in a block sans-serif font, usually red with a black outline. Its alignment varies to fit the cover illustration. The author's name is at the bottom of the cover, usually in the same font and color as the title.	Sample cover: This format is found on the original covers of volumes 1 through 11, and on a new 1933 cover for The Tower Treasure.
Examples (Click for full-size image) #7, 1929 #11, 1932

Format 2
Used from 1933 to 1936. Main features: "THE HARDY BOYS," in a block sans-serif font, is centered. (Except in the 1934 cover of The Mark on the Door, in which it appears below the title, left-aligned.) Various fonts were used for the title, ranging from the narrow lettering used for Footprints Under the Window to the wide, decorative font used for The Sinister Sign Post. The author's name is at the bottom of the cover, in a block sans-serif font. Various colours are used, co-ordinating with the cover's colour scheme.	Sample cover: This format is found on the original covers of volumes 12 through 15.
Example #13, 1934

Format 3
Used from 1937 to 1945. Main features: "THE HARDY BOYS," in various script fonts, is centered. Usually in red, white, or yellow. The title's font and alignment varies, but block sans-serif fonts in yellow, red, or white are usually used. Function words ("of", "the", etc.) sometimes appear in smaller script. The author's name is at the bottom of the cover, in various fonts. Sometimes it is broken into two lines.	Sample cover: This format is found on the original covers of volumes 16 through 24. As well, new covers for volumes 1 through 9 were released in this format.
Examples #18, 1939 #19, 1940 #21, 1942 #22, 1943 #1, 1944

Format 4
This format, which, except for the font, is the same as Format 5, was used only once: on a new 1946 cover for volume 10, What Happened at Midnight. Although this was the font's only appearance on a Hardy Boys cover, it was subsequently used for many Nancy Drew books of the period.	#10, 1946

Format 5
Used from 1946 to 1965. Main features: All elements use the same classy serif font. In the mid-fifties, the font was beefed up a bit, becoming more bold. The change was slight; however, one noticeable difference between the two fonts is the "W" (see cover examples #34 and #38 below). "THE HARDY BOYS" is aligned right, left, or center. It's usually red or yellow. The title's alignment varies. It's usually coloured white or black, and function words are occasionally a smaller size. The author's name is smaller than in other formats -- just over half the width of the cover. It's usually located on one line at the bottom of the cover. (The 1965 cover for Footprints Under the Window is an exception to this. "Franklin W. Dixon" is found on two lines, right-aligned just beneath the title. If the creators had placed the name at the bottom of the cover, it would have obscured the footprints.)	Sample cover: This was the longest-running cover format of the original series, and it's the oldest format that's still in print today. It was used on the original covers of volumes 25 through 44, as well as many new covers for older volumes: 1950: Volumes 11 through 15 1959/60: Volumes 1 through 9 1962: Volumes 11, 14, and 16 through 24 1964: Volume 6 1965: Volume 12 By 1962, all of the older covers had been replaced by covers of this format. (Except for What Happened at Midnight, which used Format 4, above, but it's arguable that Format 4 is a special case of Format 5.)
Examples #26, 1947 #14, 1950 #34, 1954 #38, 1959 #12, 1965

Format 6
Used in 1966. Main features: The structure is the same as the previous format, but the font has been switched for one that looks more modern. Franklin W. Dixon's name becomes even smaller.	Sample cover: New covers for volumes 27 and 37 were released in this format.
Examples #7, 1966 #37, 1966

Format 7
Used from 1966 to 1967. Main features: The next step in the evolution: thin horizontal lines are added above and below "THE HARDY BOYS." Besides that, it's the same as the previous format. "THE HARDY BOYS," always centered, is usually white or yellow, as is the title. The author's name is quite small. It's usually located at the bottom of the cover, sometimes on two lines instead of one. In the 1967 cover of The Mark on the Door, it's centered directly below the title, which foreshadows Format 9.	Sample cover: This format is found on the original covers of volumes 45 and 46. As well, new covers for volumes 10, 13, 17, and 21 were released in this format.
Examples #13, 1967 #46, 1967 #21, 1967

Format 8
Used from 1968 to 1970. Main features: Once again, there's just a slight change: the font is replaced with something that resembles Arial or Helvetica. Perhaps coincidentally, the variety of colours increases. On several of these covers, Franklin W. Dixon's name isn't spelled in all caps -- a first for a Hardy Boys cover.	Sample cover: This format is found on the original covers of volumes 47 and 48. As well, new covers for volumes 15, 18, 23, 25, 29, 30, 31, and 32 were released in this format.
Examples #15, 1968 #47, 1968 #18, 1969 #23, 1970

Note: Around 1970, Rudy Nappi introduced a new concept for his cover illustrations. Instead of depicting a specific scene, his new illustrations contained a montage of different elements from the book, arranged on an abstract background.

Format 9
Used from 1970 to 1974. Main features: For the first time, "THE HARDY BOYS," the title, and the author's name are all incoroprated into a single unit. The Helvetica-esque font from the previous format is retained. "THE HARDY BOYS" is centered at the top. A thin horizontal line separates it from the title, centered below it. The author's name appears beneath the title, again separated by a thin horizontal line. All elements are the same colour: either black or white.	Sample cover: This format is found on the original covers of volumes 49 through 53. As well, new covers for volumes 20, 21, 22, 26, 28, 33 through 36, and 38 were released in this format.
Examples #20, 1970 #26, 1970 #28, 1970 #38, 1973 #53, 1974

Format 10
Used from 1975 to 1979. Main features: A slight alteration of the previous format, incorporating the volume number, which appears to the left of "THE HARDY BOYS." To visually separate them, a box is drawn around the number and "THE HARDY BOYS."	Sample cover: This format is found on the original covers of volumes 54 through 58.
Examples #54, 1975 #57, 1978