My graduate school career was in BritLit, eighteenth-century division, and a paper I wrote on Boswell’s Life of Johnson was one of the few that was not contemptible. So it was with the reluctance of long-standing Johnsonian sympathies that I picked up Joshua Kendall’s The Forgotten Founding Father: Noah Webster’s Obsession and the Creation of an American Culture (G.P. Putnam’s Sons, 355 pages, $26.95).

Boswell’s portrait of Johnson makes him look heroic despite his highly evident flaws, but Mr. Kendall goes head-on in conceding by the seventh page of his biography that Webster was not a very attractive character: arrogant, pedantic, obsessive-compulsive, self-aggrandizing, combative to the point of vituperation, withdrawn, and generally off-putting.

And yet. And yet his influence on American culture has been profound and enduring. His spelling book, which sold 13 million in its various editions, became a foundation of general literacy in America. He wrote about the defects of the Articles of Confederation and campaigned energetically for the adoption of the Constitution. His work as editor of the American Minerva gave a voice to the Federalist side in the political disputes of the early Republic. He worked effectively to establish a national copyright law. He helped to found Amherst College (in part to counteract the Unitarian tendencies at Harvard, then as now a whipping-boy for conservatives).

Then there is the dictionary. It was not just a titanic achievement in lexicography, with a precision and subtlety in definition not previously achieved. It was not just that he included everyday language among formal language and expanded the general scientific vocabulary. It was the central component of his lifelong campaign to establish that there is an American language, distinct from British English, that unites the regions and ethnicities of this nation.

It displayed some of his weaknesses. While publicly disparaging Johnson’s dictionary, Webster, after the manner of all lexicographers, borrowed heavily from it. His amateur etymologies were fanciful (read: crackpot). But it became the dictionary for Americans.

Its effects endure. Though most of Webster’s proposals to reform spelling were laughed down in his time, we still spell color without a u and critic without a k. The lineal descendant of his dictionary is the massive undertaking at G.C. Merriam Co. (Since the expiration of the copyright, Webster’s has been slapped on the cover page of any number of dictionaries produced by other publishers.) Though the language that we speak and spell, American English, was sure to develop, there can be no doubt that Noah Webster helped to shape its course.

Mr. Kendall, in his enthusiasm to rehabilitate his subject’s reputation, occasionally goes too far—if Webster’s abortive plan to publish as transatlantic dictionary in England had succeeded, “Americans and Britons might today be speaking the same version of English.” Doubtful. But he writes clearly, he has marshaled his evidence, and he does not flinch from Webster’s unattractive qualities. He makes a good case.