London

"How the Chimney-sweeper's cry
Every black'ning Church appalls..."

I think William Blake's poem is about how the people of London are unhappy with their surroundings.  The "marks of woe" on their faces is a sign that they are being oppressed. The people of London have a feeling of imprisonment without physically being in prison.  "The mind-forged manacles..." creates an image of the people feeling imprisoned.  The line "Every black'ning Church appalls' makes me think that the people feel imprisoned by the Church of England.  The people were forced to be a part of the Church of England so they felt oppressed by the church. There is also a bad connotation on marriage.  The Church of England was created so King Henry could annul his marriage, so marriage is seen as a bad thing because it brought about the Church of England, causing the people's imprisonment.