The Nicaraguan poet Rubén Darío was one of the main representatives of modernism and one of the most influential authors in Spanish literature at the end of the 19th and the beginning of the 20th centuries. His own personal archives, comprised of over 5,000 documents, include material produced in 1893‒1923 related to his diplomatic and literary endeavors as well as to his private life. The typology of the documents varies: drafts, photographs, letters, handwritten notes, postcards, business cards, wills, telegrams, press clippings, official correspondence, invoices, food menus, and so forth. Among all the documents, the one that stands out is a notebook that contains autographical poems by Darío, drawings made by his son, and handwritten pieces about his most private family life. It is a school notebook with oilskin covers that Darío took on his journey to Nicaragua in 1907‒8 and then back to Spain. The condition of both the oilskin covers and the pages show evidence of time having taken its toll; they also show that, once Darío returned home, the notebook served other purposes, notably that of being a sketch pad for his son, Rubén Darío Sánchez (nicknamed “Güicho”). The notebook contains drawings, lines, and doodles in pencil made by the child on all the pages, including those that have writing by Darío. Four pages are missing at the beginning and the pagination of the notebook was done at a later stage. The first 38 pages contain a series of autographical poetic compositions by Darío, both complete and incomplete, including various edited poems (autographical versions and printed versions of some of them differ, the former being the first originals); several unpublished poems: and five stanzas of another poem. The most notable contents are “In Autumn” (pages 1‒11), which is incomplete, and the original manuscript for “Song of Autumn” (pages 13‒14). Almost at the end of the notebook (pages 41‒59) are pages copied in an uneven hand by Francisca Sánchez, possibly from a chapter of an unpublished novel by Darío, La isla del oro (Island of gold). Francisca was the poet’s partner from 1899 and it was Darío, together with Amado Nervo, who taught her how to write. On page 40 of the notebook is a curious note in Darío’s hand with the telegraphic codes that he used to communicate with his son Rubén and Francisca. After the author’s death in 1916, Francisca Sánchez kept the documents in a trunk in her home in Navalsaúz (Ávila) until 1956, when she donated them to the Spanish Ministry of National Education. The archive remained in the Faculty of Philology of the Complutense University of Madrid until 2008, when it was transferred to the Heritage Library of the Complutense University of Madrid, the institution that preserves and provides access to these documents.