Bouanchaud was born at Poydras Plantation, one of eight children of Joseph Alcide Bouanchaud, Sr. (1838-1896), and his second wife, the former Eugénia Helene Hébert (1853-1918). He graduated from Poydras Academy, [[Louisiana State University]] in Baton Rouge, and [[Tulane University]] in [[New Orleans]], from which he obtained his LL.B. degree in 1902.<ref name=lahist/> In 1908, he was elected as the state representative for Pointe Coupée Parish, at a time when each of the sixty-four parishes had at least one member elected to the state House. He was the House [[Speaker]] in his final term from 1916 to 1920.<ref>{{cite web|url=https://house.louisiana.gov/H_PDFdocs/HouseMembership_History_CURRENT.pdf|title=Membership of the Louisiana House of Representatives, 1812-2024|publisher=Louisiana House of Representatives|accessdate=June 10, 2020}}</ref>
While lieutenant governorunder Governor John Milliken Parker, Sr. (1863-1939), Bouanchaud was also elected as the president of the 1921 state constitutional convention, since updated into the current constitution in 1974. In 1924, rather than seeking reelection as lieutenant governor, Bouanchaud ran unsuccessfully for [[governor]] in the [[primary]] election but was defeated by Henry Luse Fuqua, Sr. (1865-1926) who died two years into his gubernatorial term. In 1929, with his state political career at an end and [[Huey Long|Huey Pierce Long, Jr.]] as governor, Bouanchaud was elected as district attorney for the 18th Judicial District in New Roads upon the death of Jacob Haight Morrison, III (1975-1929), the father of later New Orleans [[Mayor]] [[Chep Morrison]], who had been DA for the preceding two decades. Bouanchaud left the DA's office in 1936, resumed his law practice, and engaged also in [[farming]] and [[cattle]] raising.<ref name=lahist>{{cite web|url=https://www.lahistory.org/resources/dictionary-louisiana-biography/dictionary-louisiana-biography-b/|title=Bouanchaud, Hewitt Leonidas|publisher=''A Dictionary of Louisiana Biography'': Louisiana Historical Association|accessdate=June 10, 2020}}</ref><ref>''A Dictionary of Louisiana Biography'' used the sources for its article on Bouanchaud: Alcée Fortier, ed., ''Louisiana,'' Vol. 3 (1914);Judy Riffel, ed., ''A History of Pointe Coupée Parish and Its Families'' (1983), and Dave H. Brown, ''A History of Who’s Who in Louisiana Politics in 1916'' (1916).</ref>
From his first marriage in 1905 to the former Emma Campbell Kearney (1876-1914), Bouanchaud had three children. After Emma's death, he married in 1916 the former Eustatia Morrison (1891-1976) and had another child.<ref name=lahist/> Bouanchaud is interred beside his second wife at St. Marys Cemetery in New Roads. The first wife is interred in the same cemetery.<ref name=findagrave/> Many Bouanchaud descendants still live in New Roads. One of those descendants was James Madison Bouanchaud (1931-2020), a civic figure and [[automobile]] dealer in New Roads, who branched out into Zachary in East Baton Rouge Parish and Gonzales in Ascension Parish.<ref>{{cite web|url=https://obits.nola.com/obituaries/nola/obituary.aspx?n=james-madison-bouanchaud&pid=196311253&fhid=5614|title=James Madison Bouanchaud|publisher=''The New Orleans Times-Picayune''|date=June 7, 2020|accessdate=June 10, 2020}}</ref>