DAddario's first factory was in Lynbrook, New York, and the initial staff consisted of only five employees. As always, it was a real family operation with John, Sr., John, Jr. and James leading the company's growth and business plans. James' wife Janet helped to design packaging, heading up what would eventually become the companys art department. The printing facility was still a strong support for the fledgling company, providing a steady source of income as the family developed their superior line of strings. The D'Addario reputation for service and quality served them well as they tapped into the market with their own products. Aggressive marketing strategies would help their product line gain popularity, and the staff of five quickly multiplied to fifteen.

John, Jr. and James were intent upon expanding the company's product line. John, Sr. was a little cautious about growth and recognized that it was probably a sign that he should retire, as his own father had, and let his capable sons take the reigns. It was around this time in the early 1980s that D'Addario would complement its successful fretted line with the acquisition of the Kaplan Musical String Company, a long-established manufacturer of classical instrument strings.

The brothers embarked on a rigorous program of research and development. They created a world-renowned line of products in the field, establishing D'Addario as a premier manufacturer of bowed instrument strings. D'Addario's guitar and bass strings were already a great success. The brand was continually gaining in popularity and securing a sizeable share of the market.

In 1984, the company would relocate to a larger facility to handle the increased demand for their product, and the production staff ballooned to 150 employees. This would not be the last time the company would find itself busting at the seams of its factory space. Operations have expanded on several occasions since, with the largest expansion in 1994, when the company relocated to a new 110,000-square foot facility in Farmingdale. Today D'Addario & Company, Inc. occupies a total of 190,000-square feet and employs more than 900 people, each one of them making an invaluable contribution to what has always been a family business. A distribution center in California handles shipments to the West, Rico manufacturing facilities also in California produce the world's top reeds, and satellite offices in Chicago,Los Angeles, Austraila, Japan, France and Hong Kong cater to musicians and customers across the globe. D'Addario Canada is a third distribution center, providing D'Addario products to Canadian customers.

The research and development arm of D'Addario is one of its strongest assets. Headed by James, the engineering department has accumulated many important manufacturing and product patents in the field. The company prides itself on identifying problems in their production and implementing solutions. This includes the work theyve done on their newest product line additions, such as Evans Drumheads (1995) Planet Waves, an accessory line (1998), HQ Practice Products, drum silencing and silent practice products (2004), and most recently Rico Reeds (2004).