structural:expansion, structural:summarization
Manchester and Salford

In 1842, his parents sent the 22-year-old Engels to Salford, England, a manufacturing centre where industrialisation was on the rise. He was to work in Weaste, Salford, in the offices of Ermen and Engels 's Victoria Mill, which made sewing threads. Engels's father thought that working at the Salford firm might make his son reconsider some of his radical opinions. On his way to Salford and Manchester, Engels visited the office of the Rheinische Zeitung in Cologne and met Karl Marx for the first time. Initially they were not impressed with each other. Marx mistakenly thought that Engels was still associated with the Berliner Young Hegelians, with whom Marx had just broken off ties.

In Manchester, Engels met Mary Burns, a fierce young Irish woman with radical opinions who worked in the Engels factory. They began a relationship that lasted 20 years until her death in 1863. The two never married, as both were against the institution of marriage. While Engels regarded stable monogamy as a virtue, he considered the current state and church-regulated marriage as a form of class oppression. Burns guided Engels through Manchester and Salford, showing him the worst districts for his research.

Engels was often described as a man with a very strong libido and not much restraint. He had many lovers and despite his condemnation of prostitution as "exploitation of the proletariat by the bourgeoisie" he also occasionally paid for sex. In 1846 he wrote to Marx: "If I had an income of 5000 francs I would do nothing but work and amuse myself with women until I went to pieces. If there were no Frenchwomen, life wouldn't be worth living. But so long as there are grisettes, well and good!" His most controversial relationship was with the wife of his rival Moses Hess, Sibylle, who later accused him of rape.

While in Manchester between October and November 1843, Engels wrote his first critique of political economy, entitled " Outlines of a Critique of Political Economy ". Engels sent the article to Paris, where Marx published it in the Deutsch–Französische Jahrbücher in 1844.

Engels observed the slums of Manchester in close detail, and took notes of its horrors, such as child labour, the despoiled environment, and overworked and impoverished labourers. He sent a trilogy of articles to Marx. These were published in the Rheinische Zeitung and then in the Deutsch–Französische Jahrbücher, chronicling the conditions among the working class in Manchester. He later collected these articles for his influential first book, The Condition of the Working Class in England (1845). Written between September 1844 and March 1845, the book was published in German in 1845. In the book, Engels described the "grim future of capitalism and the industrial age", noting the details of the squalor in which the working people lived. The book was published in English in 1887. Archival resources contemporary to Engels's stay in Manchester shed light on some of the conditions he describes, including a manuscript (MMM/10/1) held by special collections at the University of Manchester. This recounts cases seen in the Manchester Royal Infirmary, where industrial accidents dominated, and which resonate with Engels's comments on the disfigured persons seen walking round Manchester as a result of such accidents.

Engels continued his involvement with radical journalism and politics. He frequented areas popular among members of the English labour and Chartist movements, whom he met. He also wrote for several journals, including The Northern Star, Robert Owen 's New Moral World, and the Democratic Review newspaper.