John Bradshaw 
Concordance to the Poetical Works of John Milton [PDF ebook] 

First published in 1894. This Concordance to the Poetical Works of John Milton includes all of Milton’s poems, excluding the Psalms and the Translations in the prose works; and all of the words are given with the exception of some of the pronouns, conjunctions, adverbs and prepositions; but any of these used peculiarly are given. It is hoped that the work will be found useful not only by the student of Milton but by the grammarian and the philologist.