William Thorndike, Jr. Biography and Net Worth

Director of Perimeter Solutions

Mr. Thorndike founded Housatonic Partners, a leading middle market private equity firm with offices in Boston and San Francisco, in 1994 and has been a Managing Director since that time. Prior to founding Housatonic Partners, Mr. Thorndike worked with T. Rowe Price Associates, a global asset management firm, and Walker & Company, a publishing company, where he was named to its board of directors. Mr. Thorndike has served as a director of over 30 companies since founding Housatonic Partners. He is currently a director of CNX Resources Corporation, a natural gas company, and serves on various boards of directors of private companies. He also serves as a Trustee of WGBH, a public broadcaster serving southern New England, and the College of the Atlantic. Mr. Thorndike is the author of “The Outsiders: Eight Unconventional CEOs and Their Radically Rational Blueprint for Success,” which has been translated into 12 languages. Mr. Thorndike holds an A.B. degree in English and American Literature from Harvard University and an M.B.A. degree from Stanford University.

What is William N. Thorndike, Jr.'s net worth?: The estimated net worth of William N. Thorndike, Jr. is at least $210.12 million as of March 5th, 2026. Mr. Thorndike, Jr. owns 8,960,656 shares of Perimeter Solutions stock worth more than $210,118,423 as of March 11th. This net worth approximation does not reflect any other assets that Mr. Thorndike, Jr. may own. Learn More about William N. Thorndike, Jr.'s net worth.
How do I contact William N. Thorndike, Jr.?: The corporate mailing address for Mr. Thorndike, Jr. and other Perimeter Solutions executives is 8000 Maryland Avenue Suite 350, Clayton MO, 63105. Perimeter Solutions can also be reached via phone at 314-396-7343 and via email at [email protected]. Learn More on William N. Thorndike, Jr.'s contact information.
Has William N. Thorndike, Jr. been buying or selling shares of Perimeter Solutions?: Over the course of the past ninety days, William N. Thorndike, Jr. has sold $5,438,500.00 in Perimeter Solutions stock. Most recently, William N. Thorndike, Jr. sold 100,000 shares of the business's stock in a transaction on Thursday, March 5th. The shares were sold at an average price of $24.06, for a transaction totalling $2,406,000.00. Following the completion of the sale, the director now directly owns 8,960,656 shares of the company's stock, valued at $215,593,383.36. Learn More on William N. Thorndike, Jr.'s trading history.
Who are Perimeter Solutions' active insiders?: Perimeter Solutions' insider roster includes Tracy Cool (Director), Jeffrey Emery (President, Fire Safety), Haitham Khouri (CEO), Vivek Raj (Director), Kyle Sable (Chief Financial Officer and Principal Accounting Officer), William Thorndike, Jr. (Director), and Jorge Valladares, III (Director). Learn More on Perimeter Solutions' active insiders.
Are insiders buying or selling shares of Perimeter Solutions?: In the last twelve months, Perimeter Solutions insiders bought shares 1 times. They purchased a total of 254,600 shares worth more than $3,559,308.00. In the last twelve months, insiders at the sold shares 12 times. They sold a total of 1,243,094 shares worth more than $22,292,270.88. The most recent insider tranaction occured on March, 5th when Director William N Thorndike Jr sold 100,000 shares worth more than $2,406,000.00. Insiders at Perimeter Solutions own 10.0% of the company. Learn More about insider trades at Perimeter Solutions.
Information on this page was last updated on 3/5/2026.

William N. Thorndike, Jr. Insider Trading History at Perimeter Solutions

Transaction Date	Buy/Sell	Number of Shares	Average Share Price	Total Transaction	Shares Held After Transaction	Details
3/5/2026	Sell	100,000	$24.06	$2,406,000.00	8,960,656
3/4/2026	Sell	125,000	$24.26	$3,032,500.00	9,060,656

William N. Thorndike, Jr. Buying and Selling Activity at Perimeter Solutions

Perimeter Solutions Company Overview

Perimeter Solutions, SA manufactures and supplies firefighting products and lubricant additives in the United States, Germany, and internationally. It operates in two segments, Fire Safety and Specialty Products. The Fire Safety segment provides fire retardants and firefighting foams, as well as specialized equipment and services for federal, state, provincial, local/municipal, and commercial customers. The Specialty Products segment produces and sells Phosphorus Pentasulfide, which is primarily used in the preparation of lubricant additives, including a family of compounds called Zinc Dialkyldithiophosphates. The company offers its products under the PHOS-CHEK, FIRE-TROL, AUXQUIMIA, and SOLBERG brands. Perimeter Solutions, SA was founded in 1963 and is headquartered in Clayton, Missouri.

Today's Range

Now: $23.45

$23.29

$23.99

50 Day Range

MA: $26.71

$23.27

$29.66

2 Week Range

Now: $23.45

$8.76

$29.88

Volume

984,040 shs

Average Volume

1,105,591 shs

Market Capitalization

$3.50 billion

P/E Ratio

N/A

Dividend Yield

N/A

Beta

1.98