The purpose of the study is to investigate the lexical characteristics of Maritime English as used in the 18th and 19th centuries through two approaches to keyword analysis: corpus frequency-based keyword analysis and text dispersion-based keyword analysis. The target corpus used in this study is an English journal corpus consisting of Captain Vancouver and Lieutenant Broughton’s expedition journal written in the late 18th and early 19th centuries. We focus on comparing important maritime-related words and essential theme-specific words used in the target corpus with those used in the BE06 corpus, representing contemporary general British English, and those used in the Contemporary Maritime English Corpus (CMEC). Through a bilateral cross-comparison of the two keyword analyses, we conclude that dispersion-based keyword analysis shows better results than frequency-based keyword analysis in that the former is more effective than the latter regarding the two criteria proposed by Egbert and Biber (2019): the content-distinctiveness of maritime-related keywords and the content-generalisability of theme-specific keywords. We also discuss some exciting findings about maritime-related keywords under a multilateral comparison of those used in the target corpus and the BE06 corpus as well as in the target corpus and the CMEC.