The merger of Canadian Pacific Railway with Kansas City Southern Railway is now official.

The fusion, under the banner of Canadian Pacific Kansas City, marks the continent’s first major railroad rail merger in more than two decades. 

It combines the two smallest of North America’s seven Class 1 railroads, after the U.S. rail regulator approved the $31-billion US deal last month.

That green light cleared the final hurdle in CP Rail’s bid to buy KCS and create the only railway stretching from Canada through to the U.S. and Mexico.

U.S. Surface Transportation Board chair Martin Oberman said in March the combined company will speed up freight travel time and encourage tighter competition with the other five, larger railways.