In 1819, the US government acquired a tract of land known as the New Purchase. As the New Purchase became subdivided, the area donned Decatur County was established in 1821, named after naval hero Commodore Stephen Decatur (who also had the honor of Decatur Co., Tennessee being named after him).

In the spring of 1822 the newly established Decatur County’s court was formed and government set up. The county seat of Greensburg was so named after one of the early founder’s hometown of Greensburg, Pennsylvania.

Early in the 1870s, observant citizens noticed a small sprig on the northwest corner of the recently constructed Courthouse tower. It soon became evident that the small sprig was thriving when additional sprouts were spotted. In all, five small trees were counted, all growing at an altitude 110 feet above the courthouse lawn.

By 1888, county officials became fearful that the growing trees might cause permanent damage to the tower roof. As a result, workers employed a steeplejack to ascend the tower and remove three of the shrubs. Of the two remaining, one ultimately attained a height of about 15 feet high with a diameter of almost five inches at the base. At the same time, another tree made an appearance on the southeast corner of the tower, growing to a considerable height. During its maturation, another tree sprung up on the southwest corner. These two new trees endured, as did the Greensburg’s nickname of "Tree City".

Today, 150 years later, Greensburg is still home to one of the original Carnegie libraries built in 1905, although the building is no longer used for that purpose. Recently the Decatur Co. Memorial Hospital was named among the top five rural hospitals in America by Progressive Farmer magazine. Honda Manufacturing of Indiana opened in late 2008 in the city to begin production of the Civic automobile. From proud beginnings, to today’s achievements, to tomorrow’s bright future, the city of Greensburg has been a work of art 150 years in the making.