This company incorporated in January, 1911. Initially MacLellan could be found at the same address as the New Werner Company. Mac Lellan published a number of the Abbott biographies most likely in the teens as part of the Everybody's Books Series. It is unclear as to which Abbott books were printed.

The 16 books known to be in this series are as follows:
Mary Queen of Scots
Josephine
Hannibal Warrior and Statesman
Cleopatra
Nero the Roman Emperor
Peter the Great of Russia
William of Normandy
Xerxes King of Persia
Henry IV
Marie Antoinette
King Darius
Alfred the Great
Alexander the Great
Elizabeth of England
Julius Caesar, Roman Ruler
Genghis Khan

I suspect the total list is the same as the 20 volume set of the Werner Company (especially when considering there was a relationship between the companies).