Colorado River Bridge at Bastrop, Historic bridge across Colorado River in Bastrop, United States

The Colorado River Bridge at Bastrop is a 1,285-foot (392 m) steel bridge over the Colorado River, made of three steel truss spans carried on concrete piers. It is one of the earliest surviving Parker truss bridges in Texas. The structure is also known as the Old Iron Bridge.

The bridge was built to handle rising automobile traffic between Houston and Austin after World War I. The Kansas City Bridge Co. won the contract; the original estimate of $45,000 rose to a final cost of $167,500, partly covered by bonds and local taxes. Completed in 1923, it opened in January 1924, and the earlier bridge was torn down in the early 1930s. It was listed on the National Register of Historic Places on July 19, 1990.

Locals call it the Old Iron Bridge, a name that distinguishes it from later crossings. It carried traffic between Houston and Austin from its opening in January 1924 until a replacement span took over; the original bridge was torn down in the early 1930s. Today it is listed on the National Register of Historic Places, designated on July 19, 1990.

The bridge is open to pedestrians and cyclists and provides a direct crossing over the river for foot traffic. The structure is easiest to walk during daylight hours when you can see the full span and river views clearly.

The Old Iron Bridge is one of the earliest surviving Parker truss bridges in Texas. Its three steel truss spans rest on concrete piers across a 1,285-foot crossing of the Colorado River, and the structure was listed on the National Register of Historic Places on July 19, 1990.