Mill Rock Packaging Acquires Keystone Paper & Box Company

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NEW YORK, Feb. 13, 2023 -- Mill Rock Packaging Partners LLC ("Mill Rock Packaging") announced today that it has acquired Keystone Paper & Box Company ("Keystone"), a leading specialty packaging company that manufactures custom folding cartons for consumer and healthcare end markets.

Mill Rock Packaging, formed by Mill Rock Capital in 2020, is a growth-oriented specialty packaging company focused on leading design, innovation and technology, with strong operational capabilities and unparalleled customer service. The transaction marks Mill Rock Packaging's expansion to the Eastern U.S. and its fourth acquisition.  In connection with the transaction, Keystone's leadership team has made a significant investment in Mill Rock Packaging. Management will remain with the company. Terms of the transaction were not disclosed. 

Keystone, based in South Windsor, CT and founded in 1944, is a leading high-end paperboard packaging company focused on premium, multi-SKU, design-intensive packaging solutions and related services, including product engineering, prototyping and production.  The company's core offerings span a broad range of high-performance, sustainable, customized folding cartons for food and beverages, pharmaceuticals, health and beauty and other daily-use products.  The company operates a state-of-the-art production facility with substantial capacity for growth.

"I am very proud of what we've achieved at Keystone since our founding by my grandfather," said Jim Rutt, President of Keystone. "Through our partnership with Mill Rock Packaging, our customers will gain access to high-quality production facilities in the Midwest and West Coast. I am delighted that Mill Rock Packaging shares our commitment to quality, integrity and service, and I look forward to future growth leveraging our combined resources."

Keystone marks the platform's initial expansion to the East Coast and will integrate with Mill Rock Packaging's other operations in the West and Midwest. The combined company will operate six production facilities offering design-intensive and sustainable paperboard packaging to an attractive range of daily needs-driven consumer markets. 

Mill Rock Packaging Chief Executive Officer Allen Ennis stated, "We welcome the customers, suppliers and associates of Keystone to Mill Rock Packaging. We look forward to accelerating growth across the platform with Keystone as our flagship East Coast production and service center, supported by continued investment into its team and capabilities."

"This is a highly strategic transaction that enables us to serve our customers from coast to coast, fulfilling Mill Rock's initial vision to create a national consumer packaging powerhouse," added Mill Rock Packaging Vice Chairman and Mill Rock Capital Senior Partner Bob Feeser. "We are excited to work with the Keystone team to advance our vision of a unified, national, specialty packaging growth platform."

Alvarez & Marsal, White & Case LLP and FINNEA Group advised Mill Rock Packaging on the transaction. Ben Markens advised Keystone Paper & Box.


Keystone Paper & Box Company is a leading specialty packaging company manufacturing custom folding cartons. The Company provides a suite of design, engineering and production services for high-end paperboard packaging.  Based in South Windsor, CT, Keystone has been a trusted partner to the food & beverage, pharmaceutical, health and beauty, and consumer goods end markets since 1944. For more information, please visit


Mill Rock Packaging Partners is a specialty packaging growth platform and a portfolio company of Mill Rock Capital. The partnership was formed in 2020 to invest in growing businesses with advanced service and product capabilities in the consumer packaging industry.  For more information, please visit


Great Mill Rock LLC dba Mill Rock Capital is a growth and operations oriented private investment firm that invests in well-positioned middle market industrial businesses in North America. Founded by Christopher Whalen and Adi Pekmezovic, Mill Rock Capital is purpose-built to invest in family-owned businesses, owner-operators and founder-led companies across six industry verticals. Focus sectors include chemicals, materials and packaging; industrial distribution; services; metals and engineered materials; transportation and logistics; and specialty manufacturing and industrial technology. This strategy leverages the deep expertise of the firm's principals, a majority of whom have direct operating experience in these same industries. Mill Rock Capital supports business transformation through a dual-sourcing strategy encompassing majority equity and Activ Capital® – debt, senior equity or hybrid investments which provide business owners value-added financial partnership without relinquishing a controlling stake. For more information, please visit

Source: Mill Rock Packaging