who journeyed to Denver, who died in Denver, who came back to Denver & waited in vain, who watched over Denver & brooded & loned in Denver and finally went away to find out the Time, & now Denver is lonesome for her heroes,
- See, we told you Denver was important to the Beats. It was located along one of the main cross-country highways, so they could have someplace to crash for a while on their frequent trips from the East Coast to the West Coast and back again.
- Eventually, however, most people left Denver, which made the city "lonesome for her heroes." Ginsberg may have Neal Cassady in mind again.
who fell on their knees in hopeless cathedrals praying for each other's salvation and light and breasts, until the soul illuminated its hair for a second,
- In a particularly "hopeless" mood, they prayed in cathedrals for "salvation and light and breasts."
- Also, the soul has hair? Who knew!
who crashed through their minds in jail waiting for impossible criminals with golden heads and the charm of reality in their hearts who sang sweet blues to Alcatraz,
- They went to jail and hoped to meet "criminals with golden heads," like the halos surrounding the heads of angels in older paintings. These criminals would pine for the famous Alcatraz prison by singing blues songs.
- We take it that they never do meet these criminals that the speaker calls "impossible."
who retired to Mexico to cultivate a habit, or Rocky Mount to tender Buddha or Tangiers to boys or Southern Pacific to the black locomotive or Harvard to Narcissus to Woodlawn to the daisychain or grave,
- Even when they retired, they were still doing crazy stuff.
- In Mexico they "cultivate a habit," likely meaning they developed an addiction to a kind of drug.
- In Rocky Mount, North Carolina, they went out in the nature to search for the Buddha. (Jack Kerouac's sister lived in Rocky Mount).
- In Tangiers, Morocco, they started love affairs with boys.
- The Southern Pacific is a railroad, so the speaker probably means they become wandering tramps.
- At Harvard they became self-centered people or "narcissists."
- At the Woodlawn Cemetery in New York, they either engaged in a group sexual activity called a "daisychain" or they are dead.
who demanded sanity trials accusing the radio of hypnotism & were left with their insanity & their hands & a hung jury,
- It's unclear whose "sanity" is being put on trial in this line.
- They accused the radio of trying to "hypnotize" them. In the end, they remain the ones who are considered "insane."