In southern Connecticut, the federal government is replacing a 118-year-old bridge along America’s busiest rail corridor. The $1.3 billion project was largely funded by the 2021 infrastructure law that was championed by then-President Joseph R. Biden Jr. — and strenuously opposed by Donald J. Trump.

These days, however, motorists cruising by the construction site might be forgiven for thinking that a certain famous New York developer was responsible for it all.

“PRESIDENT DONALD J. TRUMP” a sign by the road declares. “REBUILDING AMERICA’S INFRASTRUCTURE.”

In recent months, a number of similar signs have popped up in front of major infrastructure projects financed by the bipartisan 2021 legislation, a $1.2 trillion package that Mr. Trump, who left office in January of that year, had passionately railed against. He called the bill “a loser for the U.S.A.,” and warned that Republican lawmakers who signed on could be thrown out of office by angry primary voters. “Patriots will never forget!” he wrote.

The signs bearing Mr. Trump’s name now adorn bridge projects in Connecticut and Maryland; rail-yard improvement projects in Seattle, Boston and Philadelphia; and the replacement of a tunnel on Amtrak’s route between Baltimore and Washington, according to W. Kyle Anderson, a spokesman for the company.

In an email, Mr. Anderson said the new signs “are a voluntary Amtrak initiative, updating outdated signage posted at the project locations listed previously, following the change in presidential administrations earlier this year.”

The signs note, in a smaller font, that the projects in question are “funded by the Infrastructure Investment and Jobs Act,” the official name of the legislation that Mr. Trump tried to derail.