Henderson was a prolific author and contributed entries on Scottish figures for the Dictionary of National Biography and Encyclopædia Britannica.
He was considered an authority on poet Robert Burns and Mary, Queen of Scots.
[3] He was the second of 11 children born to farmer Archibald Henderson and his wife, Catherine (née Finlayson), both of Kincardine-in-Menteith, a village in Perthshire.
[4] He attended the University of St Andrews and joined the staff of the Encyclopædia Britannica.
"[2] Henderson was also an editor of later editions of The History of England from the Accession of James the Second, considered the foremost historic work of its era, and Minstrelsy of the Scottish Border.