| Business | Phone |
| Archer Engineers 1060 Country Club Rd, St Charles 63303 | (636) 946-7020 |
| Astec Engineering Svc Inc 1523 S Old Highway 94, St Charles 63303 | (314) 439-9600 |
| Westar Corp 4 Missouri Research Park Dr, St Charles 63304 | (636) 498-6004 |
| Schaefer Engineering 158 Hughes Ln, St Charles 63301 | (636) 916-1580 |
| Sci Engineering Inc 130 Point West Blvd, St Charles 63301 | (636) 949-8200 |
| Semke Consulting 154 Hughes Ln, St Charles 63301 | (636) 896-9995 |