The walk lasted seven hours and 17 minutes, and included a brief call with President Trump.

Such a walk was supposed to take place in March, but it was postponed because NASA did not have two appropriately sized spacesuits available. That sparked an outcry — and a “Saturday Night Live” spoof — about the legacy of sexism in the space program.

On Friday, live video of the event, which began just before 8 a.m. Eastern, showed two bulky white figures — first Ms. Koch, then Ms. Meir — working outside of the space station, which glowed against the blackness of space.

The women could be heard talking to each other, and helmet cameras showed the view as they clambered along the outside of the space station.

At one point, Ms. Meir could be seen crossing beneath the dangling feet of Ms. Koch. “Right beneath your feet, so don’t move down,” she said.

President Trump called into the space station to congratulate the crew on their achievement around 12:30 p.m. Eastern, describing the two as “brave, brilliant women.”

“Our country is very proud of you,” he said.

The president was joined by Vice President Mike Pence, NASA Administrator Jim Bridenstine and Ivanka Trump, Mr. Trump’s daughter. He said in his remarks that it was “the first time for a woman outside of the space station,” an inaccuracy that Ms. Meir gently corrected. She is the 15th woman to do a spacewalk. But until Friday, all of those astronauts had been paired with male colleagues.

“This is really just us doing our jobs,” Ms. Meir said, adding that credit was owed to the female explorers, scientists, engineers and astronauts who came before her.

The call lasted about five minutes.

Commander Luca Parmitano of the European Space Agency and Andrew Morgan, a NASA astronaut, assisted the spacewalkers from the space station. Mr. Parmitano controlled a robotics arm used in their mission, while Mr. Morgan provided airlock and spacesuit support

Ms. Meir and Ms. Koch had planned to install lithium-ion batteries on Oct. 21, but the timeline was hastened after a power controller failed last weekend. The controller, which regulates the batteries that distribute power to the station, had been in operation for 19 years and will be replaced. The agency said the failure had no impact on the crew’s safety or continuing experiments.