WASHINGTON — When Dominic Peacock found out he had been selected for an unpaid summer internship at the National Congress of American Indians here, he looked up the airfare from Albuquerque, rejected the option, and boarded a bus and rode 44 hours.

Now, after a long day thumbing through bills and working for legislation to protect tribal artifacts, he walks a few blocks to a hotel restaurant where he buses tables until 1 a.m. His workweek — 60 to 75 hours long — affords him one day off to catch up on chores in his American University dorm room and explore the city.

“This is the schedule that I want,” said Mr. Peacock, a senior at the University of New Mexico and member of the Acoma Pueblo tribe. “I’m going to finish this. I don’t care what it costs.”

Thousands of interns like Mr. Peacock have descended on the nation’s capital, hoping to gain connections and work experience answering phones, sorting mail and occasionally helping with larger projects in congressional offices, federal institutions, nonprofits and legal divisions across the city.