His credentials (from Wikipedia) -
“In 1806, Webster published his first dictionary, A Compendious Dictionary of the English Language.
“In 1807, Webster started two decades of intensive work to expand his publication into a fully comprehensive dictionary, An American Dictionary of the English Language. To help him trace the etymology of words, Webster learned 26 languages.”
“In 1825, Webster completed his dictionary during his year abroad in Paris and at the University of Cambridge.”
“In 1828, at the age of 70, Webster published his dictionary; it sold poorly, with only 2,500 copies, and put him in debt.
“In 1840, he published the second edition in two volumes with much greater success.”
George and Charles Merriam took over from there.