- 6 Silhouettes
- 11 Silk
- 1 Silk Association of America
- 7 Silk industry
- 4 Silos (agricultural structures)
- 3 Silver mining
- 2 Silver-plated ware
- 1 Silversmiths
- 7 Silverware
- 2 Silverware industry
- 2 Silverwood Street
- 20 Silverwork
- 14 Simeon (Biblical figure)
- 1 Simmon's Hardware Co.
- 1 Simmons' Patent Medicine
- 1 Simon, Apostle, Saint
- 1 Simon, of Cyrene
- 3 Simpson & Neal Shipbuilder's Yard
- 1 Simpson, Edmund Shaw, 1784-1848
- 1 Simpson, James Young, 1811-1870
- 1 Simpson's Lumber Yard
- 1 Simpson's Washington Print Works
- 3 Simpson's Wool & Cotton Factory
- 2 Sims, William S., 1858–1936
- 2 Simurgh
- 1 Sindbad the Sailor (Legendary character)
- 1 Siner Bros. Brick Yard
- 3 Singapore
- 3 Singer Manufacturing Co. Building
- 1 Singer Manufacturing Company
- 1 Singers
- 3 Singing
- 78 Single-family dwellings
- 17 Single-story
- 2 Sinks
- 1 Sir Isaac Newton
- 1 Sirens (Mythology)
- 1 Sirens (sound devices)
- 1 Sisson, James, J. L.
- 5 Sisters of Charity
