The Fight for 15 movement scored milestone victories this March as both California and New York State passed legislation to phase in a $15-per-hour wage floor over the next six years. The minimum wage in New York City will reach $15 in 2018, adding a whopping $12,000 to the annual income of workers at the bottom of the pay scale.

The victory was a reminder that the labor movement remains a formidable force that can effect change for all working people. At a time of acute income inequality, unions are essential leaders in the fight for equity.

In New York City, fast-food workers including delivery workers earn an hourly wage that can go as low as $5.45; the average yearly salary of a fast-food worker is $11,000, according to the advocacy group Fast Food Forward. A full-time job at the current minimum wage — which rose from $7.25 to $9 in January — pays only $18,720 per year, placing a single mother with two children nearly $2,000 below the official poverty line.

Labor organizers found many fast-food workers living in homeless shelters, doubled up with other family members or sleeping on the sofa in the homes of sympathetic friends. These full-time workers had to choose between rent and food. Their plight motivated the Service Employees International Union, New York Communities for Change and other unions and advocacy groups to take up the challenge of fighting for a higher minimum wage.

In 2012, the Fight for 15 was born when about 200 fast-food workers marched down Broadway in New York City. It soon went national. A wave of strikes by fast-food workers rippled across the country, bringing hundreds of underpaid workers out into the open to demand better wages — and the right to do so without fear of retaliation. In 2014, the movement went global, with demonstrations by fast food workers in Zurich and Manila.

Now that New York and California are moving toward a $15 minimum wage for fast-food workers and other hourly employees, the movement has expanded to include others fighting for better wages and the right to unionize, including home-care workers, airport workers and adjunct college professors.

The Fight for 15 reveals, for anyone who doubted, the enduring relevance of labor unions — and their ability to lift the boats of all workers.