What has become a cliché has its origins in a piece of verse by William Blake. In my ignorance too, I understood the Dark Satanic Mills as the textile factories of the Industrial Revolution where children and poor people worked inhuman hours in dangerous conditions for a pittance. Certainly those factories were as much a stain on our fair English countryside as our own modern world with its gigantic office buildings and advertisements reaching as far as our computers and homes via telephone. I have noticed how new buildings in London tend to be built from black metal and glass. But Blake seems to have had another meaning in mind.

A dear friend who studied Blake at university sees the poem Jerusalem in a deeper context, of Blake’s own writing. These mills would not have been factories,  not even churches, “but the universities of Oxford and Cambridge which were pumping out pure rationalism, killing the human spirit, and further expressed the deism of so much of the Church“. Of course we are referring to the eighteenth century, not our own time or from periods when these Universities changed with their times and assimilated aspects of changing culture.

Why describe those universities in such terms? Perhaps they were spiritually dark, devoid of God and they mass-produced like factories? I find the idea perplexing but not beyond the bounds of possibility. Perhaps the term could apply all the way across the board to the entire British Establishment of the time. A century later, Oscar Wilde wrote:

To me one of the things in history the most to be regretted is that the Christ’s own renaissance, which has produced the Cathedral at Chartres, the Arthurian cycle of legends, the life of St. Francis of Assisi, the art of Giotto, and Dante’s Divine Comedy, was not allowed to develop on its own lines, but was interrupted and spoiled by the dreary classical Renaissance that gave us Petrarch, and Raphael’s frescoes, and Palladian architecture, and formal French tragedy, and St. Paul’s Cathedral, and Pope’s poetry, and everything that is made from without and by dead rules, and does not spring from within through some spirit informing it. But wherever there is a romantic movement in art there somehow, and under some form, is Christ, or the soul of Christ.

Returning to Blake, few have read the paragraphs immediately preceding Jerusalem, the hymn set to music by Parry and conventionally sung in the spirit of British patriotism. I remember learning this poem by heart at Prep School. We understood it not so much as the freedom of our spirit but our response to the exhortations of our teachers to excel in all things and become winners in competition. Blake also expresses this contrast brought out by Wilde and others between Christianity and classical rationalism. It is difficult to imagine the Zeitgeist of those days and that stiffened human spirit and that corpse of the Renaissance that did not escape the attention of thinkers like Berdyaev.

The stolen and perverted writings of Homer and Ovid, of Plato and Cicero, which all men ought to contemn, are set up by artifice against the Sublime of the Bible; but when the New Age is at leisure to pronounce, all will be set right, and those grand works of the more ancient, and consciously and professedly Inspired men will hold their proper rank, and the Daughters of Memory shall become the Daughters of Inspiration. Shakespeare and Milton were both curb’d by the general malady and infection from the silly Greek and Latin slaves of the sword.

Rouse up, O Young Men of the New Age! Set your foreheads against the ignorant hirelings! For we have hirelings in the Camp, the Court, and the University, who would, if they could, for ever depress mental, and prolong corporeal war. Painters! on you I call. Sculptors! Architects! suffer not the fashionable fools to depress your powers by the prices they pretend to give for contemptible works, or the expensive advertising boasts that they make of such works: believe Christ and His Apostles that there is a class of men whose whole delight is in destroying. We do not want either Greek or Roman models if we are but just and true to our own Imaginations, those Worlds of Eternity in which we shall live for ever, in Jesus our Lord.

And did those feet in ancient time
Walk upon England’s mountains green?
And was the holy Lamb of God
On England’s pleasant pastures seen?

And did the Countenance Divine
Shine forth upon our clouded hills?
And was Jerusalem builded here
Among these dark Satanic Mills?

Bring me my bow of burning gold!
Bring me my arrows of desire!
Bring me my spear! O clouds, unfold!
Bring me my chariot of fire!

I will not cease from mental fight,
Nor shall my sword sleep in my hand,
Till we have built Jerusalem
In England’s green and pleasant land.

There is a Wikipedia article And did those feet in ancient time that gives us more context and explanation of the various biblical allegories Blake uses. Blake did have much to say about the industrial factories of his time and how workers were effectively enslaved by unscrupulous businessmen. The view that the term referred to churches has been in vogue, but stands up to literary criticism with more difficulty. Perhaps, the meaning is much more interior and secret in Blake’s thought.

The article contains much more, and should be studied for context. There are many references and outside links should you wish to study this subject.