He remained there eight years, combining his apprenticeship with Robinson with a part-time job in financial management at Trinity College in Hartford.

During his tenure, the governor's administrative staff was restructured, as well the state militia; and a tax commission office was founded.

Concern had been growing nationally about the mass killing of birds for hat-making uses and for food; with support from gun manufacturers and hunting organizations, McLean and Rep. John W. Weeks of Massachusetts successfully attached the Weeks-McLean Act to an appropriations bill in March 1913.

With the advice of Elihu Root, McLean immediately introduced new legislation giving the president the power to negotiate a treaty to regulate the hunting of migratory birds; this bill was passed in July 1913.

[8] McLean resumed the practice of law in Hartford, and died of heart disease in Simsbury, on June 6, 1932 (age 74 years, 243 days).

His will established the non-profit McLean Fund, which has since operated two enterprises in his home town of Simsbury - a senior living community and elder-care services provider and a private game refuge.

The McLean Game Refuge consists of over 4,200 acres (17 km2) of land in Simsbury and Granby and is open to the public; part of it has been designated a National Natural Landmark.