William Gunder came to Euphemia, Preble County, Ohio during the summer of 1816.  He became the first settler of Section 8 in Twin Township when he camped southwest of Arcanum near a tributary of Miller’s Fork in 1817.  William purchased this land in 1820 when it was offered for sale to complete the Miami Erie Canal.  He was married to Nancy Rice of Preble County in August, 1821.  They had fifteen children with ten living to become adults.  He continued to purchase other sections of land in Twin Township and in 1833 built a three room log home on his land in Section 4.  The Gunder family moved into new home during the summer of 1833 and in 1835 Caroline Gunder became the first of eight Gunder children born on land now a part of Arcanum.  This home was located on the lot now containing a home at 105 West North Street.  The property had returned to the ownership of the Gunder family in the late 1960s. 

In the fall of 1848 William requested that a town be platted by G&MRR surveyors from his wooded area.  William insisted that a unique name be selected for his new town.  After much discussion, Arcanum (a Latin word which meaning secret/ hidden) was chosen.  The original plat was filed at the Courthouse in Greenville, OH but the original document was lost or destroyed.  Then another plat made on October 27, 1849 and was recorded on  November 17, 1849 by J.C. Shepherd, Recorder of D.C.O.  It was signed by William Gunder and Geo. Faulkner, William's Son-in-Law (Dicey's husband).  William had given George the land East of Main Street on the plat after 1838 when George & Dicey were married. 

William & Huldah gave the G&M RR eight and one‑half lots from the original plat to build a water station, siding, and depot.  The G&M RR resold all but lot 32 within a year after receiving this gift from William.  He never received any of the proceeds from the sale of those lots.  The G&M RR did build their depot on lot 32 that they retained.  It remained in that location until it was demolished and the lot cleared during the 1970's. 

By the end of June l852, most of the 36 lots in the original plat were sold and William added another plat containing 23 more lots to the original town on August 9, 1852 and recorded the Gunder Addition on August 5, 1853.  Arcanum had grown to include 59 lots and the Gunder log cabin. 

William used money from the sale of lots in Arcanum to purchase hundreds of acres of land in Jay County, IN. and in Dallas and Taylor County, IA.  He also purchased 160 acres of land, in Preble County, near Lewisburg, OH and in 1852, the family moved to this farm.  His sons cared for the farm and William traveled and continued to purchase more land.  The entire family including sons and sons-in-law were involved in farming and managing his vast land holdings. 

In September 1858  he purchased 160 acres of land located just East of West Baltimore (Verona), Clay Twp., Montgomery County, OH.  William died on 13 Oct, 1863 on this land and his will, probated in Montgomery County, OH, listed it as the Gunder Homestead.  He died at the age of 66y, 7m, 3d and was buried in Ithaca Cemetery, Darke County, OH.

The Dayton Union City Railway, completed in 1852, ran through Arcanum aiding in attracting residents. Arcanum established a formal government in 1859 electing their first mayor, Mayor H. A. Kepner in 1874.

By the end of the 20th century, Arcanum boasted a population of just over 1200 residents.