The phrase "an historic step" is correct and usable in written English.
It is typically used to describe a significant or important action or decision that marks a notable change or progress in a particular context.
Example: "The signing of the peace treaty was an historic step towards reconciliation between the two nations."
Alternatives: "a significant step" or "a momentous step".
In an historic step towards proper democracy, he proposed fixing the constitution to allow more than one person to run for his office.
He said: "Today's announcement, making free school meals available to 1.4m more children, marks an historic step forward in the fight against child poverty.
Tomihisa Taue, the mayor of Nagasaki, where 80,000 died in a US nuclear attack on 9 August 1945, described Obama's decision as "an historic step".
Germany's minister for women, family affairs, senior citizens and youth, Manuela Schwesig, said the legislation passed on Friday was an "historic step" for equal rights.
Obama and supporters cast the new rules for power plants as an historic step to fighting climate change and protecting public health.
Just last month, the leaders of North and South Korea made an historic step forward in peninsular relations, on both literal and figurative grounds.
If he moves over time toward turning Morocco into a British-style limited monarchy, that might be a historic step from a stormy Arab Spring to a balmy Arab summer.
While the Oakdale and South San Joaquin irrigation districts condemned the flow proposal as "the worst kind of government overreach," a fishing group called it "a historic step to right a wrong".
"This was a big novelty, a historic step," the European official said.
The release of more than 6,000 pages of documents on Monday was hailed by victims and their advocates as a vindication and a historic step toward transparency and accountability.
In a statement, the American Civil Liberties Union called the ban "a historic step, and a clear sign that the United States continues to make significant progress toward eradicating capital punishment once and for all".
