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- Sabattus, Maine – Sabattus (Anasagunticook Indian chief)
- St. Augustine, Florida – Saint Augustine
- St. Augustine, Maryland – Augustine Herman (explorer)
- St. George, Vermont – Saint George
- St. Johnsbury, Vermont – Dr. Jonathan Arnold (member of the Continental Congress)
- St. Joseph, Michigan – Saint Joseph (indirectly, via the St. Joseph River)
- St. Louis, Missouri – Saint Louis
- St. Nazianz, Wisconsin – Gregory of Nazianzus
- St. Paul, Minnesota – Saint Paul
- St. Pete Beach, Florida – Saint Peter (indirectly, via St. Petersburg, Russia)
- St. Petersburg, Florida – Saint Peter (indirectly, via St. Petersburg, Russia)
- Salamanca (city), New York and Salamanca (town), New York – Don José de Salamanca y Mayol, Marquis of Salamanca
- Salsig, California – Edgar Budd Salsig (lumber company owner)
- San Andreas, California – Saint Andrew
- San Angelo, Texas – Carolina Angela DeWitt (wife of the city's founder Bartholomew J. DeWitt)
- San Antonio, Florida and San Antonio, Texas – Saint Anthony of Padua
- San Bernardino, California – Saint Bernardine of Siena
- San Bruno, California – Saint Bruno of Cologne (indirectly, via the San Bruno Creek)
- San Diego, California – Saint Didacus
- San Francisco, California – Saint Francis
- San Jose, California – Saint Joseph
- San Juan Capistrano, California – Saint John Capistrano
- San Leandro, California – Saint Leander of Seville
- San Lorenzo, California – Saint Lawrence
- San Lucas, California – Luke the Evangelist (indirectly, from the Spanish land grant)
- San Luis Obispo, California – Saint Louis of Toulouse
- San Mateo, California – Saint Matthew
- San Pablo, California – Saint Paul
- Sanbornton, New Hampshire – John Sanborn (grantee)
- Sanders, California – Charlotte E. Sanders (first postmaster)
- Sanford, Maine – Loleg Sanford
- Sanger, California – Joseph Sanger Jr. (Railroad Yardmaster Association secretary-treasurer)
- Sangerville, Maine – Colonel Calvin Sanger (landowner)
- Santa Ana, California and Santa Ana Pueblo, New Mexico – Saint Anne
- Santa Barbara, California – Saint Barbara
- Santa Clara, California – Saint Clare of Assisi
- Santa Monica, California – Saint Monica
- Saranap, California – Sara Napthaly (mother of a railroad man)
- Sawyers, California – Marvin L. Sawyer (first postmaster)
- Scarface, California – Scarface Charlie (a Native American warrior in the Modoc War)
- Schererville, Indiana – Nicholas Scherer (German settler)
- Schwaub, California – Charles M. Schwab
- Scott, New York – General Winfield Scott
- Scotts, California – Charles A. Scott (first postmaster)
- Scotts Corner, California – Thomas Scott, Sr. (local merchant)
- Scottsdale, Arizona – George Washington Scott
- Scranton, Pennsylvania – Selden T. and George W. Scranton (founders of the Lackawanna Steel Company and, later, the city)
- Scribner, California – Leila M. Scribner (first postmaster)
- Searsmont, Maine – David Sears (proprietor)
- Searsport, Maine – David Sears (proprietor)
- Seattle, Washington – Chief Seattle
- Sedgwick, Arkansas – Union Major General John Sedgwick
- Sedgwick, Colorado – Union Major General John Sedgwick (indirectly, via Fort Sedgwick)
- Sedgwick, Kansas – Union Major General John Sedgwick (indirectly, via Sedgwick County)
- Sedgwick, Maine – Major Robert Sedgwick
- Sedona, Arizona – Sedona Miller Schnebly (wife of the city's first postmaster)
- Seeley, California – Henry Seeley (developer of Imperial County)
- Seguin, Texas – Juan Seguin (Texas political figure and Texas Revolution patriot)
- Seigler Springs, California – Thomas Seigler (discoverer of the springs)
- Selby, California – Prentiss Selby (first postmaster)
- Selma, California – Selma Michelsen (wife of railroad employee)
- Sergeant Bluff, Iowa – Sergeant Charles Floyd
- Seward, Alaska – William H. Seward
- Seymour, Connecticut – Governor Thomas H. Seymour
- Shafter, California – Gen. William Rufus Shafter
- Shaftsbury, Vermont – Earl of Shaftesbury (note spelling)
- Shapleigh, Maine – Major Nicholas Shapleigh (proprietor)
- Sharon, California – William Sharon (financier)
- Shaver Lake, California – C.B. Shaver (irrigation company founder)
- Shaver Lake Heights, California – C.B. Shaver (irrigation company founder)
- Shelburne, 3 places in Massachusetts/New Hampshire/Vermont – William Petty, 2nd Earl of Shelburne
- Sheridan, Wyoming – General Philip Sheridan (Union cavalry leader in the American Civil War)
- Shirley, Maine – William Shirley (indirectly, via Shirley, Massachusetts)
- Shirley, Massachusetts – William Shirley (governor of Massachusetts)
- Shrewsbury, Vermont – Earl of Shrewsbury
- Shumway, California – Susie Shumway (first postmaster)
- Shutesbury, Massachusetts – Samuel Shute (governor of Massachusetts)
- Sicard Flat, California – Theodore Sicard (early settler)
- Sidney, Iowa – Sir Phillip Sidney (English author) (indirectly, after Sidney, Ohio)
- Sidney, Maine and Sidney, Ohio – Sir Philip Sidney (English author)
- Sidney, Montana – Sidney Walters (son of settlers)
- Sidney, Nebraska – Sidney Dillon (railroad attorney)
- Sidney, New York – Admiral Sir Sidney Smith
- Sikeston, Missouri – John Sikes (founder)
- Silsbee, California – Thomas Silsbee (local rancher)
- Silsbee, Texas – Nathaniel D. Silsbee (railroad investor)
- Sinton, Texas – David Sinton
- Slates Hot Springs, California – Thomas B. Slate (owner, founder)
- Slayton, Minnesota – Charles Slayton (founder)
- Sloan, Iowa – Samuel Sloan (railroad official)
- Sloat, California – John D. Sloat (Naval commodore who claimed California for the United States)
- Sly Park, California – James Sly (pioneer)
- Smartsville, California – Jim Smart (Gold Rush settler and merchant)
- Smith's Ferry, California – James Smith (founder)
- Smithfield, Maine – Rev. Henry Smith (settler)
- Smithflat, California – Jeb Smith (pioneer rancher)
- Soddy-Daisy, Tennessee – William Sodder (trading post proprietor) and Daisy Parks (daughter of a coal company manager)
- Solon, Maine and Solon, New York – Solon (statesman and poet of Ancient Greece)
- Somers, Connecticut – Lord John Somers of England
- Somersville, California – Francis Somers (coal mine founder)
- Soperton, Georgia – Benjamin Franklin Soper (railroad engineer)
- Sorenson, California – Harold Sorensen (early settler)
- South Amboy, New Jersey – James Drummond, 4th Earl of Perth (The article The Amboys contains the etymology)
- South Burlington, Vermont – Richard Boyle, 3rd Earl of Burlington (indirectly, via Burlington, Vermont)
- South Euclid, Ohio – Euclid (Greek mathematician)
- South Padre Island, Texas – José Nicolás Ballí (Padre Ballí) (Catholic priest and settler)
- South Thomaston, Maine – General John Thomas (indirectly, via Thomaston, Maine)
- Spafford, New York – Horatio Spafford
- Spalding Tract, California – John S. Spalding (founder)
- Sparks, Nevada – John Sparks
- Spence, California – David Spence (landowner)
- Spencer, Massachusetts – Spencer Phips (acting governor of Massachusetts)
- Sprague, Washington – General John W. Sprague (railroad executive)
- Spreckels, California – Claus Spreckels (sugar magnate)
- Stacy, California – Stacy Spoon
- Stafford, Humboldt County, California – Judge Cyrus G. Stafford
- Standish, California and Standish, Maine – Myles Standish
- Stanfield, Oregon – Senator Robert N. Stanfield
- Stanfield Hill, California – William Stanfield (founder)
- Stannard, Vermont – George J. Stannard
- Stark, Kansas – General John Stark (indirectly, via Stark County, Illinois)
- Stark, New Hampshire and Stark, New York – General John Stark (author of New Hampshire's motto, "Live Free or Die")
- Starks, Maine – General John Stark
- Starksboro, Vermont – General John Stark
- Starkville, Colorado – Albert G. Stark (coal mine owner)
- Starkville, Mississippi – General John Stark
- Stege, California – Richard Stege (founder and landowner)
- Stephentown, New York – Stephen Van Rensselaer (Lieutenant Governor of New York)
- Sterling, Massachusetts – General William "Lord Stirling" Alexander (Scottish expatriate) (note spelling)
- Stetson, Maine – Amasa Stetson (landowner)
- Steuben, Maine – Friedrich Wilhelm von Steuben
- Stevinson, California – James J. Stevinson (landowner)
- Stewartstown, New Hampshire – Sir John Stuart (the town was incorporated following the Scottish spelling of the name)
- Stewartville, California – William Stewart (local coal mine owner)
- Stickney, South Dakota – J.B. Stickney (railroad official)
- Stinson Beach, California – Nathan H. Stinson (landowner)
- Stockton, California – Robert F. Stockton
- Stoddard, New Hampshire – Colonel Sampson Stoddard (grantee of territory)
- Stokes Landing, California – James Johnstone Stokes (founder)
- Stonehill, California – Frances Stone (first postmaster)
- Stoughton, Massachusetts – William Stoughton (first chief justice of Colonial Courts)
- Stoughton, Wisconsin – Luke Stoughton (Englishman from Vermont)
- Strafford, New Hampshire and Strafford, Vermont – Thomas Wentworth, Earl of Strafford
- Stratham, New Hampshire – Wriothesley Russell, 2nd Duke of Bedford, Baron Howland of Streatham (note spelling)
- Strong, Maine – Caleb Strong (governor of Massachusetts)
- Strong City, Kansas – William Barstow Strong (ATSF president)
- Sturgis, Michigan – Judge John Sturgis (settler)
- Suffern, New York – John Suffern (first Rockland County judge)
- Sullivan, Maine – Daniel Sullivan (settler)
- Sullivan, New Hampshire – General John Sullivan
- Sumner, Maine – Increase Sumner (governor of Massachusetts)
- Sunderland, Massachusetts – Charles Spencer, 3rd Earl of Sunderland
- Sunol, California – Antonio Sunol (landowner)
- Surry, New Hampshire – Charles Howard, Earl of Surrey
- Susanville, California – Susan Roop (daughter of Isaac Roop)
- Sutter, California – John A. Sutter (pioneer of the California Gold Rush)
- Sutter Creek, California – John A. Sutter
- Sutter Hill, California – John A. Sutter
- Swainsboro, Georgia – Stephen Swain (state senator)
- Swan's Island, Maine – Colonel James Swan of Fife, Scotland (land purchaser)
- Sweetland, California – Sweetland brothers (early settlers)
Read more about this topic: List Of American Places Named After People