CLINTON — A purchase by Union Pacific has signaled the beginning of what could be a new train bridge across the Mississippi River.

The old train depot on 11th Avenue in Clinton is in preparation for a new bridge, but a timeline for the new bridge is uncertain, according to Calli Hite, a spokesperson for Union Pacific Railroad.

"The property was purchased as part of preparations and planning in support of the possible construction of a new rail bridge over the Mississippi River, which is currently in the initial steps of the design and permitting process," Hite said in an e-mail.

A Herald article in 2013 notes that a $400 million clear span bridge had been planned to be built to replace the current bridge but a timeline was never stated for the project.

"At this point we are only working on the design and permitting to evaluate what it will take from a time and resources standpoint to construct the bridge," Hite said.

Planning for the bridge began in 1901 and Congress eventually approved the construction of a bridge in 1907. According to Clinton, Iowa: Railroad Town, a book looking at the history of railroads in Clinton, the first train then crossed the bridge in 1909 and the bridge cost $1 million. At the time of construction, the draw span was one of the largest on the Mississippi Rver.

This was one of the three lattice spans between the Iowa shore and Little Rock island. The draw span was 464 feet in length, giving a full 200 feet on either side of the 64-foot pier when it opened, to allow the passage of boats.

An Iowa Department of Transportation report from 2009 noted the current bridge has been designated by the United States Coast Guard as a hazard to navigation. The bridge requires train traffic to stop often for river traffic underneath it.

Union Pacific also owns other parcels of land around the depot. The railroad previously purchased properties from private landowners and ADM in 2013, according to a previous Herald article.