From a 1955 Milwaukee, Wisconsin City Directory there were these listings under Transportation Lines

Acme Fast Freight Inc 527 West Fowler

Acme Transfer & Trucking Co. 1471 W Fond du Lac Av

Advance Express Co. 1006 S Barclay

Advance Transportation Co. 2115 S First

Ben-Lee Motor Service 404 N 2nd

Best Transport Co Inc 1800 S 1st

Builders Transport Corp 3930 W Villard St

C & J Transport Co. 60 E Erie

Central Wisconsin Motor Transport Co. 2029 S 1st

Clark Transport Co. 601 E Erie

Cushman Motor Delivery Co. 2003 E Kinnickonnic Av

Denver-Chicago Trucking Co. Inc 2333 W Wells

Ellott Transfer Co. 216 N Water

Express Freight Lines Inc 4600 W Burnham

Fort Transportation Service Co. 1006 S Barclay

General Expressways 1213 W Pierce

Glendenning Motorways Inc 1239 W Pierce

Gross Common Carriers Inc 4653 W Electric St

HallFreight Lines 150 S Ferry

Healzer Cartage Co. 310 W Oklahoma Av

Hillside Transit Co. 1050 E Bay

Interstate Motor Freight System 4525 W Burnham

JW Cartage Co. 4170 N 1 st

Johnson Truck Service 1006 S Barclay

Lifschultz Fast Freight 527 W Fowler

Merchants Dispatch Transportation Corp 920 E Matson

Mercury Motorways Inc 1001-A W Lafayette

Motor Transport Co 4101 W Blue Mound Av

Neuendorf Transportation Co. 645 S Water

Northern Transportation Co. 405 S 6th

Northwestern Transfer Co. 134 N Young

Olson Motor Service Inc 1228 W Bruce

Port Washington Truck Lines 1006 S Broadway

Roadway Express 1713 W Pierce

Red Arrow Express 2319 N 34th

Rockford Milwaukee Dispatch Inc 3749 N Holton

Royal Transit Inc 735 S 39th

Scherer Freight Lines 200 W Oklahoma Av

Texas Freight Co. 703 E Detroit

Universal Trans-Continental Freight Co. 703 E Detroit

West Bend Transit Service 1006 S Barclay

West Shore Express Inc 1950 S 4th

Wheeler Transportation Co. 1215 S 41st

Yule Truck Lines Inc 1229 S 41st

Under the “Trucking ” listings there are these:

Darling Freight Inc 645 S Water

Fore Way Express 1213 S 41st

Keeshin Transport System- CA Conklin Trucking 1800 S 1st

Lavery Transportation Co. 3419 w Vilet

Motor Cargo Inc 2040 W Oklahoma

Silver Fleet Trucking Co. 1956 W Canal

Spector Freight System 1001 W Lafayette

Werner Transportation Co. 145 E Anderson

Yellow Transfer Service 1620 N 11th

Ziffrin Truck Lines 2619 S 5th