| Signiant | Massachusetts |
| Significo | Texas |
| Signify Health, Inc. | Texas |
| Signifyd | California |
| Signios Biosciences | |
| Signix | Tennessee |
| SignKing, LLC | |
| SignNow | California |
| Signore Web Design | Massachusetts |
| Signos, Inc. | |
| Signpath Pharma | |
| Signpost, Inc. | New York |
| Signum | North Dakota |
| Signum.AI | New York |
| SignWell | Oregon |
| SigOpt, Inc. | California |
| Sigyn Therapeutics, Inc. | |
| SIIG, Inc. | California |
| Siilver Concepts | |
| Sijin Joseph | |
| Sikich, LLP | Illinois |
| Sikka Software Corporation | California |
| Siklu Communication Ltd | California |
| Sila | Oregon |
| Sila Nanotechnologies, Inc. | |
| SILAS Solutions | |
| Silatus, Inc. | Pennsylvania |
| SiLC Technologies, Inc. | California |
| SilcsBio, LLC | Maryland |
| Silectis, Inc. | District of Columbia |
| Silent G Creations | North Carolina |
| Silent Gorilla | |
| Silent Partner | Washington |
| Silent PC | Washington |
| Silent Push | |
| SilentSignals, Inc. | |
| SilenX Corporation | California |
| Silgan Unicep | |
| Silicon Alley Group | |
| Silicon Assurance | |
| Silicon Bayou News | Louisiana |
| Silicon Connections, LLC | California |
| Silicon Couloir | Wyoming |
| Silicon Data | |
| Silicon Desert International | Arizona |
| Silicon Designs, Inc. | Washington |
| Silicon Development | |
| Silicon Forest Electronics, Inc. | Washington |
| Silicon Foundry | California |
| Silicon Harlem | |