March 19,1990 marked another major turning point in the mill's history. Simpson Paper Company purchased the mill from Georgia-Pacific and ownership reverted back to a family held, private business. It so happens that Simpson's parent company, Simpson Investment Company, was celebrating its 100th anniversary so Chairman Furman Moseley renamed the mill Centennial Mill in honor of the occasion.
During its time as owner, Simpson provided full support to enable the mill to establish a leadership position in the technical and specialty marketplace. The replacement of the headbox on the paper machine in 1992 and many other production and quality improvements were made. Emphasis on enhancing workers' skills and improving the physical working environment led to the leadership success culminating in the prestigious award of ISO 9002 Quality Certification in 1995.
Throughout the early to mid 90's hopes were high. Simpson was investing significantly in the long-term prospects of the mill. Its energy independence was a big draw and a new gearbox was installed for the No. 1 turbine. Additionally, the old wooden dam was removed and a $4,500,000 concrete dam was put up in its place. This new dam included air bladder flash boards which should eliminate the loss of water after ice out when they would normally be waiting for the boards to be reset.
In the late 90's 'Paperless Office' and similar buzz words were sweeping the industry and paper making was shifting to lower cost production and paper machines twice the size of Gilman's single paper machine. At least partially due to this situation, Simpson was not able to maintain the success of the mill and in 1999 it was forced to close.