Johnson birdied his last three holes of the third round Sunday morning for a five-shot lead, stretched it to nine shots and coasted home to an even-par 71 and a five-shot victory in the Genesis Open.
Johnson became the 20th player to reach No. 1 since the world ranking began in 1986, and he ended Jason Day's 47-week stay at the top.
The U.S. Open champion also got that elusive victory at one of his favorite courses. He had chances to win four of the last five years, and this one was never in doubt.
Johnson went 49 straight holes without a bogey until a sloppy finish that didn't matter.
