Jacobson, 61, is joining BMO Financial Group (TSX:BMO) in October. He'll be based in Chicago, his hometown, where BMO's main U.S. operations are headquartered.
His tenure in the post was marked by several significant bilateral accomplishments, said Maryscott Greenwood, managing director on international trade with McKenna Long and Aldridge in D.C.
"He presided over big developments on the bilateral front, including the Beyond the Border initiatives and the presidential permit for the new Detroit crossing," she said in an interview.
"He was extraordinarily successful in helping to forge strong ties between the Obama administration and the Canadian government. BMO is lucky to get him."
Jacobson, U.S. envoy for four years, is a Windy City lawyer who worked as a major fundraiser for Barack Obama as the junior Illinois senator ran for president in 2008. Jacobson arrived in Ottawa in October 2009 after the U.S. Senate signed off on his nomination.
While a new U.S. ambassador has yet to be officially announced, another top Obama fundraiser — Bruce Heyman, also from Chicago — is the reported front-runner.
Sources in D.C. say Heyman is Obama's first pick, but add that his nomination won't necessarily be a cakewalk given enduring Republican animosity towards the president.
Public records show that Heyman, a partner at investment firm Goldman Sachs, and his wife, Vicki, have been donating to Obama since 2007. They are what's known as "mega-bundlers" in American political parlance — in other word, top fundraisers.
Both Heymans served on Obama's National Finance Committee in 2012, helping to raise millions for his re-election campaign. The Chicago Tribune described Vicki Heyman as among the "local workhorses of the campaign ... regularly at Obama headquarters" in a report last July.
The Heymans were in attendance for a Rose Garden dinner for German Chancellor Angela Merkel in June 2011.
Heyman has been with Goldman Sachs since 1980. For 12 years, he's helmed the firm's Midwest private wealth-management group, covering 13 states and the western half of Canada.
Heyman has publicly sung the president's praises, an uncommon practice among Goldman Sachs executives. While the company was a big Obama donor in 2008, executives were angered by what they perceived as regulatory attacks from the White House and personal attacks on their character, and donated instead to Mitt Romney and the Republican party in 2012.
"I am sensitive to the emotions" of Wall Street, Heyman told the Wall Street Journal last year.
"But if you look at the facts, Mr. Obama is pro-business."
In a statement Tuesday announcing his departure, Jacobson said he'd "treasure this experience forever."
He added he was "profoundly grateful" to Obama for appointing him to the job, and thanked Prime Minister Stephen Harper for allowing him to "make a difference for our two countries."
Jacobson also praised "the kindness, the graciousness, and the generosity of spirit for which Canadians are famous."
Bill Downe, BMO president and chief executive, said Jacobson's "deep knowledge" of Canada-U.S. relations make him particularly qualified for the role.
Note to readers: This is a corrected story. An earlier version said Jacobson would be joining the bank's board of directors.