This chapter adopts a historicist focus on Blake’s professional networks in the eighteenth-century London print world, tracing a series of cartographic encounters across Blake’s involvement in the print and book trades. The survey of these cartographic encounters centres particularly on the workshop of James Basire and the bookselling and publishing business of Joseph Johnson. Throughout this chapter, the streets of London emerge as a fundamental anchor for Blake’s life, work, and imaginative enterprise. Even in these professional microcosms, however, Blake would have come into contact with cultures of the past, through antiquarian texts and monuments, and with the wider world, through geography textbooks, travel accounts, and other printed books and artworks which visualised and propagated Britain’s expanding imperial and commercial activities in the eighteenth century, all of which find renewed and transformed articulation in Blake’s illuminated books. Key figures introduced in this chapter include antiquary Richard Gough, print-seller Carington Bowles, mathematician John Bonnycastle, and map-engraver Thomas Conder. At the heart of the chapter is an effort to reframe eighteenth-century map-making—as undertaken by Blake and his contemporaries alike—as a fundamentally networked, collaborative, and often highly creative undertaking.