[5] In 1934, Chase, Harris, Forbes dissolved its banking affiliates and Macomber became chairman of the First Boston Corporation.

[2][3] In 1927, Macomber was named chairman of the board of directors for the planned sports arena at North Station which became the Boston Garden.

The board, which consisted of members of the Madison Square Garden Corporation, the Boston and Maine Corporation, and a number of Boston businessmen, also included Tex Rickard, Homer Loring, George Hannauer, Edward Lawrence Logan, Louis K. Liggett, Charles F. Adams, Huntington Hardwick, and Joseph Gilman.

[10][12] On September 3, 1920, Massachusetts State Treasurer Fred J. Burrell resigned following an investigation by a special legislative committee and Governor Calvin Coolidge appointed Macomber, Albert P. Langtry, and Henry A. Wyman to administer the office until a successor could be confirmed.

[3] Beginning in 1956, the closing race of Suffolk Downs' spring meeting was called the John R. Macomber Memorial Handicap.

[3] In 1928, Macomber's horse Bridge won the inaugural Master of Foxhounds Association Steeplechase for hunters in front of a crowd of 10,000 at Pimlico Race Course.

Beginning in 1927, Macomber opened Raceland to the public free of charge for one day of the annual horse meet.