Benton County was formed on December 21, 1837 from sections of Dubuque County. It was named after Thomas Hart Benton, lawyer, colonel in the War of 1812, and Senator from Missouri for a period of 30 years.

According to the U.S. Census Bureau, the county has a total area of 718 square miles, of which 716 square miles is land and 2.2 square miles is water.

The Benton County Courthouse, located in Vinton, was built in 1906. It was listed on the National Register of Historic Places in 1976 as a part of the County Courthouses in Iowa Thematic Resource. The courthouse is the fourth building the county has used for court functions and county administration.

• A site for the county seat was selected by the special commissioners on the first Monday in May 1846, and called Northport. The town was laid out early in the summer, and later in the same year notices were posted for bids to build a hewed-log courthouse, two stories in height and 20' x 24' in size.
• The walls of the building were laid in 1846 or 1847. District court was first held in the log cabin of an early settler, Thomas Way. The cabin was located about two miles northeast of the present site of Vinton. The log structure did not have a roof or floor, so the court met in a log home during inclement weather.
• The name of the county seat was soon changed from Northport to Fremont, in honor of General John Charles Fremont (1813-1890). However, there was another town in Iowa named Fremont so, on February 12, 1848, the name of the county seat changed again-this times to Vinton, after Ohio Congressman Plynn Vinton who paid $50 (to be invested in town lots) for the honor.
• While the original courthouse was commenced in the 1840's, no more than a skeleton of the two-story frame building was put up until 1851 or 1852 when work on it was finally resumed. However, it was never really occupied as a completed structure because of a dispute over the location of the county seat before it was destroyed by fire in January 1853. The fire was said to have been started by a strong wind blowing on some ashes and coals which had been removed from the stove and thrown outside near a pile of wood shavings left under the building by workmen. The county records were saved by the county treasurer and the district clerk, who happened to be sleeping in the office on the second floor.
• That fall, bonds were issued (at 10 percent interest) for a $7,000 courthouse to be built on the old site. The cornerstone was laid July 13, 1856, under the auspices of the Masonic fraternity, and "such deposits as the fraternity or any of the citizens chose to make" were placed inside the cornerstone. According to the Vinton Semi-weekly Eagle of January 10, 1905, "The occasion was of great interest to the citizens of Vinton and of Benton County generally." Following the ceremony and the speeches, the day's activities were enlivened by a "fine brass band, which dispensed strains of their soul-stirring music at intervals..."
• Construction on this first permanent courthouse to be erected in Benton County was far enough advanced by the following Christmas season that the courthouse was dedicated at a grand ball and elaborate dinner on December 23, 1856. Given by citizens of Vinton and vicinity, this "house warming" was attended by guests from towns as far away as Cedar Rapids and Waterloo.
• This substantial, two-story brick structure, 40' x 60', finally cost about $13,000. It was situated in the public square, at the center of the business section of town, and the grounds were attractively landscaped.
• When the time came to replace the old brick courthouse, there was great excitement on the day the cornerstone was opened, as there had been a persistent rumor that the contents included a liquor bottle that would have been 49 years to age. The disappointment was just as great when no bottle was found. Only a few trifles were secreted within the cornerstone, the most valuable were a few old coins.
• The fourth courthouse was begun in 1905 and completed the following year. C.E. Bell and M.S. Detweiler were the architects and George Richman and Sons were the builders. Constructed of Buckeye gray sandstone, the three-story building, 112' x 77' is situated on the site of the previous courthouse, and cost $150,000. A tower, 112 feet high, contains a clock and a 1,500-pound bell donated by Paul Correll, local merchant, farmer, and property owner. On the hour, the bell rings with a resounding B flat.
  • The courthouse clock was wound manually once each week until the late 60's or early 70's when it was electrified. The bell went silent in the early 1980's when it's cabling was disconnected. The clock stopped working sometime in 2008. A complete restoration of the clock and bell started underway in October 2014 and re-installed in August 2015.
• The list of items placed in the cornerstone of the present courthouse includes the proposition for building the courthouse and the official vote of the November 8, 1904 election; the minutes of the meeting of the board of supervisors at which the contract was awarded; assessment records (1855 to 1905); statistics on population and schools in Benton County; directories and financial reports; a photograph of the previous courthouse; church histories; rosters of Civil War veterans and of the Iowa National Guard from Benton County; a G.A.R. bronze button; various U.S. coins; lists of state, county, and municipal officials; various newspapers; a New Testament; and an 1878 history of Benton County.
• There are 3 murals painted in the courthouse, when the courthouse was built. No record of the artist exist. The East mural is the old Urbana bridge, South mural is the old Belle Plaine bridge and the West mural is the old Vinton bridge. The murals were restored in 1991.