Terence Crawford closed the show by landing 47 of 77 power shots over last 2 rounds. Jeff Horn managed 59 punches thrown over last 2 rounds.
It was business as usual for Crawford, who landed 48% of his power punches after landing 48% in his last 10 fights.
More business as usual for Crawford: Horn landed 6.4 punches per round vs. Bud, whose last 10 opponents land 7 punches per round.
Terence Crawford punished Jeff Horn en route to a ninth-round technical knockout on Saturday to seize the Australian's World Boxing Organization welterweight world title.
America's Crawford, the former undisputed super lightweight world title holder, outclassed the Aussie who was defending the title he won in a huge upset of Manny Pacquiao in July of last year in Brisbane.
Horn defended the belt with a technical knockout of Gary Corcoran in December, but he was dominated by Crawford all the way at the Grand Garden Arena in Las Vegas.
Crawford, who improved to 33-0 with 24 knockouts, battered Horn for eight rounds, knocking him down in the ninth with a flurry of blows.
Horn beat the count, but Crawford unleashed another barrage and referee Robert Byrd called a halt at 2:33 of the round.
With the win Crawford claimed a world title in a third weight division.
He defeated Julius Indongo last August to become the undisputed super lightweight world champion.
A former WBO lightweight world champ, Crawford made the move up to welterweight in impressive fashion.
He won every round and was never really hurt by Horn, who fell to 18-1 with one draw and 12 knockouts.
A vocal Australian contingent among the crowd of 8,112 lustily backed Horn, but he was in trouble from the start as Crawford caught him with a hard left just seconds in.
Crawford, using his speed and his ability to switch stances to good effect, landed almost at will, Horn absorbing the punishment without finding a way to answer.