Drawing on Brian Larkin’s concept of ‘infrastructural poetics’, this article considers and compares a selection of English- and Welsh-language poems, by writers including Eliza Mary Hamilton, Frederick Faber, Richard Llwyd, and Eben Fardd, about two nineteenth-century infrastructures that transformed North Wales and Great Britain’s relationship to Ireland: the Menai Suspension Bridge (1826), and the Britannia Tubular Bridge (1850). I argue that these non-canonical poems complement perspectives derived from parliamentary records, official reports, technical planning documents, scientific manuals, and journalism, enhancing our understanding of the nineteenth-century infrastructural imagination. Specifically, building on the association of infrastructural development and modernity, I explore how the poems under discussion participate in nineteenth-century negotiations about Wales’s place and future in the United Kingdom, and how these negotiations evolved between 1819 and 1852. I show that, although Wales was the site of impressive engineering feats and accelerating industrial extraction, English-language poems present the Menai Bridge in picturesque terms, drawing on popular images of the Celtic fringe that evoke timeless, ideal beauty. Anglophone verse about Britannia Bridge, by contrast, focuses explicitly on the infrastructure’s technological modernity but claims it as an English landmark. Both strategies, I suggest, effect an erasure of Wales – as a distinct cultural and political entity – from a future conceived as Anglo-British. Poems written in Welsh, and the work of Welsh writers in English, complicate this picture, not because they reject British nationalism and imperialism, but because they seek to embed a modern Welsh nation more centrally within those political and ideological frameworks.