The Trump administration has carried out its 13th federal execution since July, an unprecedented run that concluded just five days before the inauguration of President-elect Joe Biden - an opponent of the federal death penalty.
Dustin Higgs, convicted in the killings of three women in a Maryland wildlife refuge in 1996, was the third to receive a lethal injection this week at the federal prison in Terre Haute, Indiana.
President Donald Trump's Justice Department resumed federal executions last year following a 17-year hiatus. No president in more than 120 years had overseen as many federal executions.
Higgs, 48, was pronounced dead at 1.23am on Friday (local time).
The number of federal death sentences carried out under Mr Trump since 2020 is more than in the previous 56 years combined, reducing the number of prisoners on federal death row by nearly a quarter.
It's likely none of the around 50 remaining men will be executed anytime soon, with Mr Biden signalling he will end federal executions.
The only woman on death row, Lisa Montgomery, was executed on Wednesday for killing a pregnant woman, then cutting the baby out of her womb and claiming it as her own. She was the first woman executed in nearly 70 years.
In October 2000, a federal jury in Maryland convicted Higgs of first-degree murder and kidnapping in the killings of Tamika Black, 19; Mishann Chinn. 23; and Tanji Jackson, 21.
His death sentence was the first imposed in the modern era of the federal system in Maryland, which abolished the death penalty in 2013.
Higgs' lawyers argued it was "arbitrary and inequitable" to execute Higgs while Willis Haynes, the man who fired the shots that killed the women, was spared a death sentence.
The federal judge who presided over Higgs' trial two decades ago said he "merits little compassion".
"He received a fair trial and was convicted and sentenced to death by a unanimous jury for a despicable crime," US District Judge Peter Messitte wrote in a 29 December ruling.
In a statement after the execution, Higgs' lawyer Shawn Nolan said his client had spent decades on death row helping other inmates and "working tirelessly to fight his unjust convictions".
"The government completed its unprecedented slaughter of 13 human beings tonight by killing Dustin Higgs, a black man who never killed anyone, on Martin Luther King's birthday," Mr Nolan said.
"There was no reason to kill him, particularly during the pandemic and when he, himself, was sick with COVID-19 that he contracted because of these irresponsible, super-spreader executions."
