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Guatemala City —

In the bracing morning air, workers leave their homes in the outer suburbs and hurry toward the industrial buildings lining the Guatemalan capital’s highways.

Some go by foot. Others by motorcycle; whole families on the school commute, children in their mothers’ arms. Many more travel on old yellow school buses, imported from the United States after decades of service.

The workers are almost entirely women, ranging from their late teens to early 60s. They stream into factory buildings past heavy metal gates and 10-foot walls topped with barbed wire.

What happens inside these garment factories, known as “maquilas” throughout Central America, is largely hidden from public view – even though they employ tens of thousands of workers and are crucial to Guatemala’s economy.

It is estimated Guatemala's maquilas, some pictured here, employ at least 180,000 people. CNN

Cameras and other recording devices are not allowed inside, several of the workers told CNN. Independent inspectors are hamstrung by factory bosses, according to government officials. Trade unions are few and attempts to organize are met with threats, firings and, in some cases, violence, the workers said.

What does emerge from these factories is box after box of garments overwhelmingly destined for the US: clothes for some of the biggest brands in North America, such as Carhartt, Target and Ralph Lauren, among others.

After decades of nearshoring policies pursued by successive US administrations, Guatemala has become an integrated hub for cheap apparel – and some of the consequences for the local workforce have been brutal.

A months-long investigation by CNN gathered dozens of testimonies of workplace abuse. Workers spoke of public dressing-downs and threats to fire staff unable to fulfill impossible quotas, wage theft and sexual harassment.

“If you don’t keep up, they flag you out, they discipline you.” Worker Rosa Guerra

Some maquila workers told CNN they were given daily quotas of thousands of apparel items, and made to stand for up to 15 hours a day, while earning a minimum wage of less than $500 a month.

“If you don’t keep up, they flag you out, they discipline you,” said on