P
- Pacheco, California – Salvio Pacheco
- Paducah, Kentucky and Paducah, Texas – Chief Paduke
- Painesville, Ohio – General Edward Paine (early settler)
- Parkman, Maine – Samuel Parkman (proprietor)
- Parkston, South Dakota – R.S. Parke (landowner) (note spelling)
- Parlier, California – I.N. Parlier (first postmaster)
- Parsonsfield, Maine – Thomas Parsons (proprietor)
- Pasco County, Florida – Samuel Pasco, United States Senator from Florida
- Paterson, New Jersey – William Paterson
- Patten, Maine – Amos Patten (settler)
- Patterson, New York – Matthew Paterson (early farmer) (note spelling)
- Patton Township, Pennsylvania – Colonel John Patton (co-owner)
- Paulsboro, New Jersey – Samuel Phillip Paul (son of a settler)
- Pawling, New York – Catherine Pauling (a misprint caused the U to change to a W and the name stuck)
- Payson, Arizona – Levi Joseph Payson (Illinois congressman)
- Peabody, Massachusetts – George Peabody (philanthropist)
- Pelham, Massachusetts – Henry Pelham (Prime Minister of the United Kingdom)
- Pelham, New Hampshire – Thomas Pelham-Holles, 1st Duke of Newcastle
- Pelham, New York – Pelham Burton (tutor of Thomas Pell)
- Pembroke, Georgia – Pembroke Whitfield Williams (early resident)
- Pembroke, New Hampshire – Henry Herbert, ninth Earl of Pembroke
- Pendleton, Oregon – George H. Pendleton (Democratic candidate for Vice-President in the 1864 presidential campaign)
- Pennsylvania – William Penn (Penn's Woods)
- Pentz, California – Manoah Pence (founder, first postmaster)
- Pepperell, Massachusetts – Sir William Pepperrell (hero of the Battle of Louisburg)
- Perkins Township, Maine – Thomas Handasyd Perkins
- Perris, California – Fred T. Perris
- Perry, Maine and Perry, Ohio – Commodore Oliver Hazard Perry (hero of the War of 1812)
- Perry, Florida – Madison Stark Perry, fourth Governor of the State of Florida, Confederate States Army colonel
- Perrysburg, Ohio – Commodore Oliver Hazard Perry
- Perth Amboy, New Jersey – James Drummond, 4th Earl of Perth (The article The Amboys contains the etymology)
- Peterborough, New Hampshire – Lieutenant Peter Prescott (land speculator)
- Petersburg, Alaska – Peter Buschmann (Norwegian immigrant)
- Petersburg, California – Peter Gardett (early merchant)
- Petersburgh, New York – Peter Simmons (early settler)
- Phillips, California – Joseph Wells Davis Phillips (founder)
- Phillips, Maine – Jonathan Phillips (grantee)
- Philipsburg, Montana – Philip Deidesheimer (mining engineer)
- Philipsburg, Pennsylvania – James and Henry Philips (settlers)
- Phillipston, Massachusetts – William Phillips, Jr. (lieutenant governor of Massachusetts)
- Phillipsville, California – George Stump Philipps (early settler)
- Phippsburg, Maine – Sir William Phips (colonial governor of Massachusetts) (note spelling)
- Piercy, California – Sam Piercy (early settler)
- Pierre, South Dakota – Pierre Chouteau, Jr.
- Pieta, California – Chief Pieta (local chief)
- Pike, New Hampshire – Alonzo Pike (producer of sharpening stones and tool and cutter grinders)
- Pikesville, Maryland – Zebulon Pike (American soldier and explorer)
- Pine Hill, California – Safford E. Pine (local dairy farmer)
- Pittsburg, New Hampshire – William Pitt, 1st Earl of Chatham
- Pittsburgh, Pennsylvania – William Pitt, 1st Earl of Chatham
- Pittsfield, 4 places in Maine/Massachusetts/New Hampshire/Vermont – William Pitt, 1st Earl of Chatham
- Pittsfield, Illinois and Pittsfield, New York – William Pitt, 1st Earl of Chatham (indirectly, via Pittsfield, Massachusetts)
- Pittsford, New York – William Pitt, 1st Earl of Chatham (indirectly, named by Colonel Caleb Hopkins after his hometown of Pittsford, Vermont)
- Pittsford, Vermont – William Pitt, 1st Earl of Chatham
- Pittston, Maine – John Pitt (settler)
- Plant City, Florida – Henry B. Plant
- Plattsburgh (city), New York and Plattsburgh (town), New York – Zephaniah Platt (landowner)
- Pleasanton, California – Alfred Pleasonton (Union Army general)
- Pocatello, Idaho – Chief Pocatello
- Poland, Maine – Chief Poland
- Polk County, Florida – 11th President of the United States, James Knox Polk
- Pomfret, Vermont – Earl of Pomfret
- Pomins, California – Frank J. Pomin (first postmaster)
- Pontiac, Illinois and Pontiac, Michigan – Chief Pontiac
- Pooler, Georgia – Robert William Pooler (railroad employee)
- Pope Valley, California – William Pope (land grantee)
- Port Arthur, Texas – Arthur Edward Stilwell (founder)
- Port Kenyon, California – John Gardner Kenyon (founder)
- Port Jervis, New York – John Bloomfield Jervis (engineer with the Delaware and Hudson Canal)
- Port Richey, Florida – Captain Aaron M. Richey
- Porter, Indiana – Commodore David Porter
- Porter, Maine – Dr. Aaron Porter (proprietor)
- Portola, California – Gaspar de Portolà
- Portola Valley, California – Gaspar de Portolà
- Post Falls, Idaho – Frederick Post (lumber mill builder)
- Posts, California – William Brainard Post (homesteader)
- Potter, California – Richard R. Potter (first postmaster)
- Potter Valley, California – William and Thomas Potter (early settlers)
- Poultney, Vermont – William Pulteney, 1st Earl of Bath (note spelling)
- Powellton, California – R.P. Powell (early settler)
- Pownal, Maine and Pownal, Vermont – Thomas Pownall (royal governor of the Massachusetts Bay Colony) (note spelling)
- Prather, California – Joseph L. Prather (early rancher)
- Prentiss, Maine – Henry Prentiss (landowner)
- Presho, South Dakota – J. S. Presho (early settler)
- Preston, Minnesota – Luther Preston (millwright)
- Prince Frederick, Maryland – Frederick, Prince of Wales
- Princeton, Maine – Rev. Thomas Prince (indirectly, via Princeton, Massachusetts)
- Princeton, Massachusetts – Rev. Thomas Prince
- Proctor, Vermont – Senator Redfield Proctor
- Prosser, Washington – Colonel William Farrand Prosser (homesteader)
- Provo, Utah – Étienne Provost
- Pulaski, 6 places in Georgia/Illinois/New York/Tennessee/Virginia/Brown County, Wisconsin – Casimir Pulaski (Revolutionary War hero)
- Pulaski Township, Ohio – Casimir Pulaski (Revolutionary War hero)
- Pullman, 3 places in Michigan/Washington/West Virginia – George Pullman
- Pullman, Chicago – George Pullman and Solon S. Beman
- Purser, California – Edward T. Purser (rancher)
- Putnam, Connecticut – Israel Putnam
- Putnam County, Florida – Benjamin A. Putnam, Florida legislator, first president – Florida Historic Society
- Pylema, California – Mary R. Pyle (early settler and postmaster)
- Prince's Lakes, Indiana Howard Prince Founder
Read more about this topic: List Of American Places Named After People