A historic iron bridge has taken people over Mill River since 1888, but it is proving unable to cross a deeper divide. It’s the gap between the struggling West Side and the thriving downtown; between longtime residents and newcomers; between the haves and the have-nots. Through its stages of deterioration, the bridge has been closed to cars, shored up as a pedestrian crossing, replaced with a “temporary” prefabricated walkbridge, and now abandoned in a sorry state. West Side residents and their supporters say no one cared about the West Main Street bridge before the then-deteriorating downtown was turned around. Luxury apartment high-rises went up, and city officials began spending millions of dollars to reroute the stagnant Mill River and rebuild what had been a neglected, crime-ridden Mill River Park. One is to restore the historic elements of the bridge and rebuild it to support two lanes of car traffic. The prefabricated walkbridge would be removed. Estimated cost: $6.7 million. The other is to take down the iron bridge and remove the trusses, installing them as a historic artifact in the park. The prefabricated walkbridge would remain. Estimated cost: $1.2 million.