The communication of the uncertainty of a scientific finding largely determines whether that information will be translated to practice. Unfortunately, however, our ability to study these phenomena is restrained since existing uncertainty corpora are limited in their number of full text articles and in their provision of a historical perspective. We describe a historical corpus evaluating uncertainty markers through a random sample of 167 years (1840–2007) of articles published in the British Medical Journal. Randomization was stratified from four distinct time periods, namely 1840–1880, 1881–1920, 1921–1960, and 1961–2007. Each full-text article was tagged by a group of analysts associated with a physician. We describe extensive data on the distribution of each of these linguistic markers. Contrary to our initial hypothesis, the rates of  uncertainty markers have remained surprisingly stable over the period studied in this project, except for the modal verbs in the simple present, which occur with a minor frequency in the first time period compared to the other three.