| S & S EQUIPMENT INCLawton, IA | 1306968 | 2 |
| S R ANDERSON INCBeaman, IA | 579046 | 8 |
| SAAR TRUCKING INCTreynor, IA | 3343240 | 14 |
| SABER TOWING AND RECOVERY LLCDe Witt, IA | 4371442 | 1 |
| SAM TRUCKING LLCSioux City, IA | 3836599 | 5 |
| SAUER TRUCKING INCHospers, IA | 1424766 | 9 |
| SAUNDERS SHIPPING SOLUTIONS LLCCoralville, IA | 4240583 | 3 |
| SAVITS TRUCKING INCOgden Iowa, IA | 993007 | 5 |
| SCB TRANSPORTATION LLCWaterloo, IA | 3555600 | 268 |
| SCHMIDT DAIRY EQUIPMENT LTDKeswick, IA | 188459 | 5 |
| SCHOENROCK TRUCKING LLCSioux City, IA | 4150212 | 1 |
| SCHRADER EXCAVATING AND GRADING COMPANYWalford, IA | 1718149 | 72 |
| SCHROEDER TRUCKING CORPElma, IA | 721128 | 7 |
| SCHULTZE TRUCKING INCAlgona, IA | 933819 | 66 |
| SCHUMACHER TRUCKING LLCHolstein, IA | 2267386 | 1 |
| SCHUPAN - IOWA LLCDes Moines, IA | 3909257 | 2 |
| SCHUSTER COMPANYLe Mars, IA | 69852 | 502 |
| SCHWEITZBERGER TRUCKING LLCKingsley, IA | 1828966 | 5 |
| SCOTT PIPPERT TRUCKING INCElberon, IA | 925832 | 3 |
| SDRT LLCSlater, IA | 4236580 | 6 |
| SEARS MANUFACTURING CODavenport, IA | 363493 | 3 |
| SEEGERS TRUCK LINE INCDenver, IA | 1783 | 15 |
| SHAKAKONYup, IA | 2044002 | 1 |
| SHAM TRANSPORTATION LLCDes Moines, IA | 3169884 | 3 |
| SHAW TRANSPORTATION LLCIowa City, IA | 3103752 | 1 |
| SHAWN GJERDE LIVESTOCK INCAnkeny, IA | 1274273 | 1 |
| SHERBONDY GARDEN CENTER INCCouncil Bluffs, IA | 1117606 | 3 |
| SHIMON TRUCKING LLCRolfe, IA | 1019611 | 11 |
| SHINE BROS CORPSpencer, IA | 248637 | 19 |
| SHIVAM TRANSPORT LLCClive, IA | 3274156 | 7 |
| SILVERBACK LOGISTICS LLCWaterloo, IA | 4351375 | 1 |
| SIMON'S TRUCKING INCFarley, IA | 164492 | 129 |
| SIOUX RIVER CONSTRUCTION INCSioux City, IA | 2910141 | 4 |
| SMITH TANDEM TRUCKING LLCBettendorf, IA | 4559236 | 2 |
| SMN TRANSPORT LLCMarion, IA | 3820452 | 2 |
| SNOW MOUNTAIN TRANSPORTATION LLCHumboldt, IA | 1703355 | 1 |
| SOIL SOLUTIONS TRUCKING LLCOnawa, IA | 1036891 | 10 |
| SOLE TRANSPORT LCDes Moines, IA | 231451 | 293 |
| SOLUTIONS DCT LLCDes Moines, IA | 4520145 | 1 |
| SONSON TRUCKING LLCCedar Rapids, IA | 4410877 | 35 |
| SPEEDY GO TRANSPORTATION LLCKingsley, IA | 3680921 | 1 |
| SSS HOLDINGS LLCSioux City, IA | 4389040 | 63 |
| STA-BILT CONSTRUCTION COMPANYHarlan, IA | 188470 | 72 |
| STEEL TRUCKING INCNew Sharon, IA | 779362 | 10 |
| STEVEN K OTTE TRUCKING LLCNorth English, IA | 1101077 | 1 |
| STEVEN MATTHEW WIERSMASanborn, IA | 1813867 | 1 |
| STOCKTON TOWING INCSioux City, IA | 1902220 | 52 |
| STOM CONSTRUCTION LLCCouncil Bluffs, IA | 4533244 | 1 |
| STRAITLINE TRANSPORTATION LLCBurlington, IA | 988981 | 58 |
| STS EXPRESS INCClinton, IA | 3591417 | 25 |
| STUTSMAN TRANSPORTATION INCHills, IA | 1122151 | 52 |
| SUDBECK TRUCKING INCSheldon, IA | 1031499 | 46 |
| SUKUP MANUFACTURING COMPANYSheffield, IA | 1829 | 68 |
| SUMMA LOGISTICS INCBurlington, IA | 2876280 | 41 |
| SUMMIT CONCRETE INCBettendorf, IA | 1649438 | 98 |
| SUPERIOR WELDING SUPPLY COWaterloo, IA | 1830 | 24 |
| SURPASS TRANSPORT LLCBuffalo Center, IA | 4505680 | 9 |
| SVOBODA FAMILY TRUCKING LLCHavelock, IA | 4515087 | 1 |
| SYL TRANSPORTATION LLCSioux City, IA | 3111328 | 2 |