The bell tower of Boott Cotton Mill No. 6 summoned thousands of Lowell Girls to their looms, signaled lunch break, and gave them leave to go home

Lowell, Mass., was once a city of bells. But not church bells. Starting at 4:10 in the morning, the bells of six giant mill complexes crowded along a short stretch of the Merrimack River tolled at intervals throughout the day and evening . Each pattern of clangs conveyed its own message, heard all over town. By the thousands, what came to be called Lowell girls – young women ages 14 to 30 from rocky farms throughout the Northeast – rose, trudged to work at the mills, hurried back to their rooms for lunch, and quit at the end of their 13-hour workdays to the peal of those same bells.

Workers at these looms threaded fibers pulled from cotton bales shipped from the American South. The young employees constantly checked for broken or twisted fibers and changed bobbins and shuttles

Chelmsford, as Lowell was first known, bloomed thanks to a sly industrial spy. While vacationing in Britain in 1811, Francis Cabot Lowell toured Manchester's great textile mills. He was forbidden to take notes, but he applied his remarkable photographic memory toward each detail of the turbines and clacking looms. Lowell and his partners then returned to America and copied the operations, which thrived thanks to the ready availability of southern cotton.

At the Boott Cotton Mills, the largest complex in Lowell, three-fourths of its 2,200 workers were women.

This young woman was photographed at a Massachusetts cotton mill – possibly in Lowell – in the early twentieth century.  The work was hard on the eyes, ears and back, and the hours were long

There, in 1899, Lucy Larcom wrote that "although the noise in the weave room was deafening, its incessant discords could not drown out the music of my thoughts."

Lowell declined rapidly after World War II, as owners shut the mills and headed south, where land was cheap, rivers were ice-free, and labor was non-union. Faced with a dying city, Lowell's leaders turned the entire town into an industrial museum. The National Park Service bought 88 looms and made Boott Cotton Mill No. 6 the centerpiece of the tourist experience.

Though impressive, those looms are now silent. But walking among them, visitors can imagine the ear-splitting clatter that drove row after row of Lowell girls into the music of their thoughts.