What were they thinking? Fifty years after the destruction of Portland’s Union Station, we are still asking.

Learning the lessons that came from the bitter loss of Union Station, a one-of-a-kind monument to American industry, has animated planning discussions in the city for the last half century. It has led to the start of the local historical preservation movement, which has managed to save a number of beloved local buildings over the years.

Portland wouldn’t be the Portland we know today if plans to level much of the Old Port or the West End had been allowed to go through, and the modern city’s residents benefit from the restraint that came after the shock of losing Union Station and its subsequent replacement with an ordinary shopping plaza.

Through its ongoing work, Greater Portland Landmarks has been able to identify and fight for historical buildings that not only give the city character, but also contribute to its bottom line.

We shouldn’t be too hard on our forebears who came up with the plan to level Union Station, however. They were forward-looking and optimistic people and probably could not conceive of the idea that something new would not be better than something old. Many of us have lost that sense of optimism, to our detriment.

And the need to preserve historic buildings shouldn’t be the only lesson we learn from the sad destruction of Union Station.

While almost everybody now agrees that it was a horrendous mistake to tear the station down, back then it was considered a wise move by the city’s leaders. This episode should remind us to listen to the outnumbered skeptics who speak up when all the smartest people around are convinced they know what they’re doing.