Alexander McNair was the grandson of David McNair, a Scotch Covenanter who emigrated from County Donegal, Ireland, before 1737 and settled in what is now Dauphin County, Pennsylvania.
He was the son of David and Ann (Dunning) McNair and was born on his father's farm in Mifflin (now Juniata) County, Pennsylvania. After his father's death in 1777, his mother took him to live near Pittsburgh, where he grew up and obtained some education.
In 1799, McNair became the first lieutenant in the United States Army. When the army was reduced he was discharged in June 1800, and in 1804, he moved to St. Louis. At the March 1805 term of the court of common pleas he was appointed one of the associate judges and from that time until his death he held public office continuously.
Aside from the governorship, the principal offices he held were those of city trustee, sheriff of St. Louis County, colonel, then adjutant and inspector of territorial militia, United States marshal, register of the St. Louis land office, and federal agent to the Osage Indians. He also engaged in various mercantile pursuits and acquired a good deal of property. As governor from 1820 to 1824 he urged no startling policies.
Although McNair was a member of the constitutional convention, he played an unobtrusive part in its deliberations, except in his opposition to the constitutional provision for a high salary schedule for state officials. Before the convention adjourned he announced himself as a candidate for governor against William Clark. He had greater gifts of popularity than Clark, and he conducted an extensive personal campaign. His opponents, led by the St. Louis machine, charged that he lacked education and ability for such an office, that he had used his authority in the land office loosely in order to gain popularity, and, as the campaign grew hotter, that he was using the "greatest exertions in the tippling shops" of St. Louis. Nevertheless, he was elected by a majority of 4, 020 in a total of 9, 132 votes.
Although brought up as a Presbyterian and, during his earlier years at St. Louis, an active member of a Masonic lodge, before his death he received the last rites of the Roman Catholic Church of which his wife was a member.
McNair opposed any restriction on slavery, but in order to hasten her admission into the Union he approved Missouri's adroitly worded "Solemn Public Act. " He was careful to observe all the proprieties connected with the inauguration of the new state government and took great pains to study and lay before the assembly copies of the laws of the older states.
His messages to the legislature were clear, brief, and conservative in tone, and they dealt with subjects appropriate to a new frontier state, such as fiscal affairs, immigration, relations with the Indians, the militia, and the industrial development of the commonwealth.
In March 1805, McNair was married to Marguerite Susanne de Reilhe, the well educated and talented daughter of a prominent French merchant who had died three years earlier, gave him standing within the most influential political circles of the city. She, with eight of their ten children, survived him.
