From 1813 to 1830, the county initiated several changes to its government.
By an act of the territorial legislature, the Court of Quarter Sessions was succeeded by a panel of three judges of common pleas in 1813.
Two years later, this panel was succeeded by a newly created county court in 1815, composed of justices of the peace elected from the county to three-month terms.
The St. Louis County Circuit Court (established in 1815 as the judicial branch of the county) was given authority in 1816 over the executive and legislative affairs of the county, superseding the court of justices of the peace.

In 1821, a hybrid County and Probate Court was established and given executive and legislative control, and in 1830, its probate functions ceased.
This County Court operated as the government of St. Louis County until public scandals encouraged the state legislature to abolish it and replace it in 1859 with a Board of Commissioners.

Sessions of the County Court and other county governing bodies were held in a variety of locations during this early period.
The Court of Quarter Sessions held its first meeting in 1804 at a tavern in St. Louis, then regularly at a building at Third and Plum until 1817.
The county seat moved that year to a newly built one-story log cabin on Third Street between Elm and Spruce, followed by a move to the brick Baptist Church at Third and Market in 1820.
The County Court established a commission in 1822 to study a permanent courthouse (previous facilities were rented), and in 1823, Auguste Chouteau and John Baptiste Charles Lucas donated two tracts of land that formed a vacant square bounded by Broadway, Fourth, Chestnut, and Market.

Between the summer of 1826 and 1833, on this vacant tract was built a low-roofed two-story brick structure fronting Fourth Street that was the first permanent courthouse for St. Louis County.
Within a few years, however, the building's size was inadequate for the county government's needs; the original building was left in place during construction on the new building, which began in 1839.
This new courthouse, now known as the Old Courthouse, included a finished rotunda, dome, and west wing by 1843; the 1833 courthouse was demolished in 1851, and by 1856, the east wing was complete.
From 1813 to 1830, the county initiated several changes to its government. By an act of the territorial legislature, the Court of Quarter Sessions was succeeded by a panel of three judges of common pleas in 1813. Two years later, this panel was succeeded by a newly created county court in 1815, composed of justices of the peace elected from the county to three-month terms. The St. Louis County Circuit Court (established in 1815 as the judicial branch of the county) was given authority in 1816 over the executive and legislative affairs of the county, superseding the court of justices of the peace.
In 1821, a hybrid County and Probate Court was established and given executive and legislative control, and in 1830, its probate functions ceased. This County Court operated as the government of St. Louis County until public scandals encouraged the state legislature to abolish it and replace it in 1859 with a Board of Commissioners.
Sessions of the County Court and other county governing bodies were held in a variety of locations during this early period. The Court of Quarter Sessions held its first meeting in 1804 at a tavern in St. Louis, then regularly at a building at Third and Plum until 1817. The county seat moved that year to a newly built one-story log cabin on Third Street between Elm and Spruce, followed by a move to the brick Baptist Church at Third and Market in 1820. The County Court established a commission in 1822 to study a permanent courthouse (previous facilities were rented), and in 1823, Auguste Chouteau and John Baptiste Charles Lucas donated two tracts of land that formed a vacant square bounded by Broadway, Fourth, Chestnut, and Market.
Between the summer of 1826 and 1833, on this vacant tract was built a low-roofed two-story brick structure fronting Fourth Street that was the first permanent courthouse for St. Louis County. Within a few years, however, the building's size was inadequate for the county government's needs; the original building was left in place during construction on the new building, which began in 1839. This new courthouse, now known as the Old Courthouse, included a finished rotunda, dome, and west wing by 1843; the 1833 courthouse was demolished in 1851, and by 1856, the east wing was complete.
St. Louis County, Missouri