In the nineteenth century, English scholars like Alexander Ellis, Walter Skeat, and Henry Sweet pioneered empirical work on English. Ellis had begun to investigate regional pronunciation as early as 1848, before the development of the International Phonetic Alphabet and sound recording, and he published his findings as On Early English Pronunciation, with Especial Reference to Shakspere and Chaucer. Skeat wrote hundreds of short etymological pieces that eventually formed the basis of his four-part An Etymological Dictionary of the English Language (first published as Etymological English Dictionary). Henry Sweet, the phonetician who inspired George Bernard Shaw’s Henry Higgins (in Pygmalion), contributed the comprehensive A History of English Sounds from the Earliest Period, covering phonetics, writing, and the stages of the language.
The earliest American scholar of Old English may have been Thomas Jefferson, who planned to write an Anglo-Saxon grammar but never did. Typical of nineteenth-century efforts was George Marsh’s The Origin and History of the English Language, and of the Early Literature It Embodies, which was devoted mostly to literary analysis from Norman times to the Elizabethan Age (which Marsh saw as the language’s pinnacle). Marsh’s work illustrates two misguided but common themes—that the only language worth studying is the literary language, and that the only language worth studying is British English.
By the late nineteenth century, more sophisticated works appeared, for example, Oliver Emerson’s The History of the English Language and Thomas Lounsbury’s History of the English Language, neither of which gave any attention to American English. Emerson focused on the details and mechanisms of change, with a good eighty pages on sound changes, grammatical analogy, and the leveling of word endings. Lounsbury divided his study into external and internal history, the former dealing with historical events (invasions, conquests) and the latter with the development of the grammatical forms of words. Emerson and Lounsbury emphasized the continuity of Anglo-Saxon with later English, in contrast to Marsh who saw it as primitive because of its lack of a literary standard.
 Stanley R. Hauer, “Thomas Jefferson and the Anglo-Saxon Language,” PMLA 98 (1983): 879-98, is the classic study of Jefferson’s Anglo-Saxonism. Jefferson’s efforts are also discussed in Andresen’s Linguistics in America, 1769-1924 and Frantzen’s Desire for Origins (both discussed in this essay).