The "Steamboat Bill" Memorial Bridges are two bridges that span one of the widest points along the Tennessee River within the city of Decatur, Alabama, between Morgan County, and Limestone County. One is a cantilever truss, and the other is a reinforced concrete. The bridges carry US 31, US 72A, and State Route 20 from the intersection of Wilson Street (US 72A, and SR 20), and 6th Avenue (US 31) in northeast Decatur.

The first bridge built here was the William Keller Bridge, completed on February 12, 1928. This drawbridge, originally served both directions.

In 1961, a new cantilever truss bridge was built to serve as a northbound contpainion to the span. The Keller Bridge was then closed for extensive renovation, when it reopened in 1964, it was converted to only carrying southbound traffic, and the new bridge carried the northbound traffic.

By the late 1970s, it became apparent that the Keller Bridge was obsolete and outmoded. Additionally, starting in the 1980s, the currents of the Tennessee River changed and running barges through the narrow gap created by the drawbridge became more dangerous, this resulted in the bridges being hit several times by barges. Also, with the amount of traffic carried by the road, the drawbridge could produce mile-long traffic jams. In 1999 the new concrete bridge opened. Northbound traffic was shifted to the new bridge, southbound traffic was moved to the rehabbed cantilever bridge, and the Keller Bridge was closed permanently and later demolished. There are additional pictures and information about the Keller Memorial Bridge available from the Historic American Engineering Record at the Library of Congress.dge

The city of Decatur is currently working with the Decatur Area Metropolitan Planning Organization (MPO), who themselves have teamed up with TTL, Inc., on a study to find a way to alleviate the increasing amount of traffic on the bridges. This is especially the case with the cantilever truss bridge that carries southbound traffic, since it cannot be widened and is outdated. Previously, ALDOT estimated in 2014 that a new toll bridge across the Tennessee River would cost $444 million, but local opposition caused that proposed project to be cancelled in January 2015. Following its approval by the city council, a $2 million feasibility study began in January 2023, at which point public input was requested. Options include building a new bridge on another location and replacing the current bridge with another one. The study time period was extended to December 2023 in August. Additionally, an extension of I-565 is proposed and the routing would possibly utilize the bridge as well.

• List of bridges documented by the Historic American Engineering Record in Alabama
• List of crossings of the Tennessee River