WASHINGTON — President Obama did a favor for his No. 2 yesterday by designating a 1,100-acre national monument in the home state of Vice President Joe Biden, using an executive action that bypasses the legislative process.

The move will fulfill a longtime wish of Biden’s to create a national park within his tiny state of Delaware — the only state without one, despite its original-colony status.

Legislation has already moved through a Senate committee to create a national park there, but Obama’s order obviates the legislative need, relying on authority granted by the 1906 Antiquities Act. Congress can still make the site a national park in the future now that it’s already owned by the feds.

Biden was on hand for the White House ceremony.