Philip Patrick Henry Cronin (August 7, 1846 – May 4, 1889) was an Irish immigrant to the United States, a physician, and a member of Clan na Gael in Chicago.

[2] Cronin's murder caused a public backlash against secret societies, including protests and written condemnations by the leadership of the Catholic Church.

After criticizing the leadership of the Chicago camp of Clan na Gael, he was expelled from the group and accused of being a British spy.

Born on August 7, 1846, in Buttevant, County Cork, Ireland,[4] Cronin was an infant when his family relocated to New York City.

After working for the St. Louis and Southeastern Railroad as a city ticket agent, Cronin secured sponsorship from the Bagnal Timber Company to study at Missouri Medical College.

Cronin was involved with the revival of the St. Louis College of Physicians and Surgeons, and he served as its professor of eye and ear diseases by the early 1880s.

[6] Clan na Gael was an oath bound secret society of Fenians devoted to Irish independence from the British Empire.

The organization engaged in large amounts of fundraising, but under the leadership of Alexander Sullivan, the Clan took a more paramilitary role in the fight for Irish independence.

[4] By the early 1880s, Cronin had determined that in order to gain a more prominent position within Clan na Gael, he needed to be near Sullivan and to move to Chicago.

[8] Cronin sought to rise through the ranks of the Chicago camp of Clan na Gael, which brought him in contact with the Triangle.

The dynamite campaign consisted largely of terrorist attacks on public spaces in Great Britain,[8] including the 1885 bombing of the Tower of London and House of Commons.

[7] This personal feud culminated in 1888,[4] when Cronin publicly accused Sullivan of embezzling $100,000 from Clan na Gael's pension fund for the families of deceased and incarcerated "dynamiters.

"[9] Hoping to settle the feud and bring Clan members back together, leaders of both factions agreed to an internal investigation.

[8] Clan na Gael members organized an internal trial, held in New York City, to investigate the charges against Sullivan.

[4] The dynamite campaign failed in large part because of the British spy Henri le Caron, who posed as a French-Irish member of Clan na Gael.

In response, Sullivan shared alleged British Intelligence reports that le Caron had provided and which named other spies, Cronin among them.

[9] On March 20, 1889, Martin Burke, going by the name Frank Williams,[12] rented a cottage in suburban Lake View, now the Uptown neighborhood of Chicago, one block from the offices of O'Sullivan Ice Company.

Burke told his landlord that his brother and invalid sister would be moving in with him and furniture, including a large trunk, was delivered to the cottage.

[13] On the night of May 4, 1889, a man called on Cronin at his home, seeking medical care for an injured worker at O'Sullivan's ice house in Lake View.

[9] Henry M. Hunt reported that Theo Conklin did some investigating, and drove to Lake View to question O'Sullivan about the accident call.

[9] Around 2 a.m. on May 5, two Lake View police officers witnessed a carpenter's wagon carrying a large trunk speeding north on Clark Street.

Lake View Police Captain Villiers examined the trunk and concluded that an adult person had been murdered and stuffed inside.

[19] Police searched the brush, grass, and vacant houses for a mile surrounding where the trunk was found, but discovered no trace of any body.

The owner of the stable told Chief of Police George W. Hubbard, on the night Cronin disappeared, a man named "Smith," referred by Detective Coughlin, rented a white horse and buggy.

On June 11, Chicago police arrested Alexander Sullivan, but only held him for one night on account of the lack of evidence of his involvement.

[9] Frank Woodruff and John Beggs, members of Clan na Gael Camp 20, were also arrested in June for their involvement in Cronin's murder.

[8] According to Henry M. Hunt, the murder of Cronin ranked in national importance with the assassinations of Abraham Lincoln and James A. Garfield, as the gruesome crime was an international sensation.

In 1929, for the fortieth anniversary of Cronin's death, the Chicago Tribune ran a contest in which readers asked to "solve the mystery of the case" for a $500 prize.

Feehan produced a long report about "the criminal acts of Clan na Gael" for Cardinal Giovanni Simeoni.

Pope Leo XIII subsequently granted Archbishop Feehan all means necessary to declare that Clan na Gael was in opposition to the Church.