The Museum portion of the OPOMAC utilizes the area that once housed the mail boxes that served Graham for fifty-seven years.  Displayed are many artifacts of Young County history.  The area includes the Native American Reserve of Young County, the dream of the Graham brothers' creation of the city, ranching history of the county, and the beginning of the Texas Cattle Raisers Association.

Young County history comes alive with the many permanent exhibits of photographs of oil fields of the 1800s and 1900s.  A military collection of uniforms and field equipment date from the American Indian War through the years of the modern American military.  Included in the exhibit is art work from a 1940s POW Camp. Photographs from the 1920s depict the culture of the city, the history of the beginnings, the trials of growth, and the enjoyment that citizens of Young County received during the time period.

The community continues to grow and support the Old Post Office Museum & Art Center by donating and loaning many wonderful artifacts to enhance the experience of the OPOMAC.  This helps keep the history of Young County, Texas, alive.