The Decatur Union Depot Museum in Decatur, Morgan County, is a historic railroad depot and transportation museum that seeks to illuminate the area's transportation heritage. Constructed in 1905, "Union Station" as it was originally known, was designed by famous southern architect Frank Milburn and constructed by the Southern Railway Company as a passenger station and depot. It remained in use as a passenger station until 1979 and was listed on the National Register of Historic Places in 1980. Despite this recognition, it fell into disrepair and was eventually abandoned. The building was later renovated and converted into a transportation museum and city offices in 2015.

Over the years, Union Station has been visited by several famous guests including Pres. Franklin Delano Roosevelt and entertainer Elvis Presley. As a result of its location, the station quickly became the focal point of business and commerce in Decatur, attracting six nearby hotels. It remained in constant use until the 1950s when the growth of automobiles and highways led to a sharp decline in travel by train. Union Station however, continued to be used as a passenger station until 1979 when Amtrak cancelled its final passenger route in north Alabama, the Floridian passenger train. Just one year later, the now defunct station was listed on the National Register of Historic Places and it remained vacant for the next 35 years.
In 2009, the process of renovating the Union Train Depot began when the Decatur City Council voted to accept a $750,000 grant from the Alabama Department of Transportation for the project. Work on the renovations began in early 2015 and it was renovated in three parts. Half of the building—the middle room where the passengers waited to board—became a museum. The wings on the north and south sides now house two Decatur police units, the school resource division, and the traffic division. The total estimated cost for the renovation was $2.5 million, half of which was financed by the city and the other half from grants and private donations. The building was officially dedicated on March 26, 2016. The new museum was awarded the Historic Preservation Project of the Year for Public Buildings by the local revitalization organization Alabama Main Street in 2016.
The new Decatur Union Depot Museum was developed under the guidance of city historian David Breland and focuses mainly on the area's railway heritage. Exhibits include model trains and train sets, railroad-related artifacts, and graphic panels that tell the history of rail service in the area dating back to the 1830s. The lobby of the museum includes a number of scenes and artifacts from Decatur businesses of the early 1900s that surrounded the depot. The main museum artifact room includes the original ticket office and a model train layout depicting Decatur along with artifacts and railroad signage. It also contains benches and the superintendent's desk from the original Union Depot and a depot desk from the Tuscumbia, Colbert County, depot from the 1920s. The museum also includes a theater that contains artifacts such as antique toy trains and railroad tools as well as audio/video presentations on Decatur's railroads. Behind the depot is the original, though renovated, loading dock that includes an original 1905 baggage cart and a number of artifacts.
The museum is located as 701 Railroad Street NW. It is open Monday through Friday from 10:00 a.m. to 3:00 p.m. Admission is free. Outside the museum, a historic marker commemorates the 1833 Tuscumbia, Courtland & Decatur Railroad that operated the first steam locomotive west of the Allegheny Mountains. Nearby are the Old State Bank Museum, the Carnegie Visual Arts Center, the Morgan County Archives, Alabama Center for the Arts, Cook Museum of Natural Science, and Princess Theatre.