In the late 19th century, he became a political ally in the Republican Party of William Madison McDonald, a prominent African-American politician.

After his mother's death in 1916 and his inheritance of half her fortune, Green built a mansion in Round Hill, Massachusetts.

[6] He went to Terrell, Texas, and turned the ailing enterprise into "a model railroad boasting the first electrically-lighted coaches in the State.

In 1896, he began a long-lasting political partnership with William Madison McDonald, an African-American leader of the Black and Tan faction of the Republican Party from Fort Worth.

He told her that he received "thousands of letters" from women offering to marry him and that "a secretary had been appointed to take charge of this class of mail."

"[10] As Hetty strongly opposed his marrying, he waited until after her death in 1916 to wed his longtime companion, Mabel E. Harlow, a former prostitute.

In addition to the various other homes he already owned, after his mother's death, Green built a mansion in Massachusetts, Round Hill,[6][11] and another on Star Island, Florida.

[3] The Round Hill mansion was designed by the Anglo-American architect Alfred C. Bossom and completed in 1921 at a cost of $1.5 million.

[18] In 1924, Green rescued the last American wooden whaling vessel of the 19th century, the bark Charles W. Morgan, and exhibited her, embedded in sand, at Round Hill.

In June 1922, the Round Hills Radio Corporation was incorporated under a commercial charter, with Colonel Green the company president.

In September 1922, the Round Hills Radio Corporation received licenses for a broadcasting station, WMAF, in addition to one for experimental work, with the call sign 1XV.

[22] Professor Edward L. Bowles set out to determine the signal strength and radiation patterns of different antenna arrays in 1926.

Round Hill's radio station (which included an early radio telescope, built atop a water tower designed to look like the foundation of a lighthouse) followed Donald B. MacMillan's and Admiral Richard E. Byrd's polar expeditions, tracked the Graf Zeppelin dirigible during its maiden transatlantic flight, and was the sole communication link for areas devastated by the Vermont floods in 1927.

[5] Green had persuaded Mabel to sign a prenuptial agreement, which limited her to a $1,500 monthly stipend, but she challenged it in court.