For many Americans, Thanksgiving is synonymous with domestic leisure — turkey roasting in the oven, football on TV, family gathered around the dining table.

But across the United States, millions of people spend at least part of the holiday at work — doctors, firefighters, police officers, reporters, waiters, cashiers, gas-station attendants, concession-stand operators, professional athletes.

The reasons people work on Thanksgiving are as varied as the jobs themselves: to make a little extra money, to satisfy the demands of an overbearing boss, to keep the community safe. For some, Thanksgiving duty is a hardship, or at least an inconvenience. At many workplaces, however, employees have forged holiday traditions out of a shared obligation, organizing office dinners and pie-making contests or inviting family members to visit.

“It doesn’t seem like I’m spending time away from my family,” said Olivia Marshall, a nurse who spent Thanksgiving working in the cancer unit at Massachusetts General Hospital. “It’s like I’m with another part of my family.”