PHILADELPHIA (CBS) – Philadelphia Mayor Jim Kenney, along with State Senator Andrew Dinniman and leaders of the region’s Irish community gathered at West Laurel Hill Cemetery in Lower Merion Sunday to memorialize 57 Irish workers who died in 1832 building the railroad from which then Main Line got its name.

With the sounds of bagpipes and gunshot salutes, the workers who all died within six weeks of arriving on the docks in Philadelphia were remembered in speeches and readings of Irish poetry at a memorial site inside the cemetery that was first dedicated five years ago.

After they died working in horrific conditions in the searing summer heat in 1832, the bodies of the workers were tossed into a pit, their deaths kept secret for nearly 180 years, until a team of researchers uncovered a secret file.

The team excavating from 2004 to 2012, finally began uncovering remains, studies indicating the seven workers found had, in fact, been murdered, shot or beaten to death — most likely by vigilantes fueled by hatred of immigrants, the Irish,Catholics and fear of their spreading cholera.

So far the remains of two workers have been identified and they have been given proper burials at special ceremonies in the country they left, but would never see again. Five other sets of remains are now at the memorial in West Laurel Hill Cemetery.

Fifty other workers remain unaccounted for as each day, Main Line trains roll past their still hidden grave on the rails they died building so long ago.