When the Civil War began, Governor Morgan named Arthur the acting assistant quartermaster general with the rank of brigadier general.  Arthur effectively administered the provisioning of food, shelter, clothing, and equipment for over 200,000 military recruits in New York.  He acted as lobbyist at the state capitol for legislation that mandated the inspection of forts and other wartime military necessities.  He did not see battle, but was promoted swiftly to inspector general, and then quartermaster general in July 1862.  With the election of a Democratic governor, Horatio Seymour, Arthur lost his commission on January 1, 1863, and did not reenlist.

Arthur became increasingly involved in Republican machine politics in New York.  He collected assessments (a percentage of the salaries that patronage appointees were expected to pay into the party’s coffers) as well as contributions from military contractors seeking to buy political influence.  By 1868, he was aligned with the Republican political machine of Senator Roscoe Conkling of New York, and backed the policies of President Ulysses S. Grant (1869-1877).  As counsel to the New York City Tax Commission (1869-1870), Arthur worked for William Tweed, the notorious boss of Tammany Hall, the major Democratic machine in New York City. 

In 1871, Senator Conkling secured his protégé the prized patronage position of Collector of the New York Customhouse.  As the largest federal office in America, the New York Customhouse collected 75% of the country’s custom duties, worth nearly $2 million annually, and provided approximately 1,000 patronage jobs.  To civil service reformers, it was a symbol of the corrupt and inefficient patronage system.  As collector, Arthur was the nation’s highest-paid civil servant.  Despite his association with shady characters and politicos, his own decorum and education earned him the nickname “Gentleman Boss.”

In 1877, the new Republican president, Rutherford B. Hayes, initiated a probe of the New York Customhouse.  The investigating commission faulted customhouse practices and its leadership, recommending the establishment of merit-based civil service rules to replace the patronage system.  Hayes sought to cushion the blow by offering Arthur a consulate in Paris.  Arthur’s refusal led the president to remove him from office on July 11, 1878.  He returned to his private law practice in New York. 

Arthur and the Conkling machine redoubled their political efforts and scored valuable victories in the 1879 New York state elections.  They were unable to gain a third-term nomination for Grant at the 1880 Republican National Convention, but when delegates turned to the compromise candidate from Ohio, James Garfield, Arthur was selected as the vice presidential nominee to give the ticket factional and geographic balance.  During the campaign, Arthur raised huge amounts of money for the Republican Party in New York, and that key state proved to be the Republicans’ thin margin of victory in the general election in November.

Once the new administration was sworn into office, the New York Customhouse controversy resurfaced, this time between President Garfield and Senator Conkling.  Vice President Arthur openly supported Conkling, but Garfield prevailed in his appointment of a reformer to the post of port collector, and Conkling resigned his senate seat.  A few months later, the nation was shocked when Garfield was assassinated by a disgruntled and delusional office-seeker.  On September 20, 1881, a somber Arthur took the presidential oath of office at his home in New York City, a pledge he repeated in the nation's capital two days later.  Expectations for the new president were low not only among reformers and other critics, but even among his friends; as one exclaimed, “Chet Arthur president?  Good God!” 

President Arthur, however, took the responsibility of the office seriously as he attempted to rise above partisan politics.  The former patronage czar endorsed civil service reform and in 1883 signed the Pendleton Act, which established the beginning of a merit-based federal bureaucracy.  In 1882, Arthur signed into law the Chinese Exclusion Act, which banned immigration from China for ten years, after vetoing a stricter version.  He also vetoed a costly Rivers and Harbors Bill, considering it to be pork-barrel legislation, but Congress overrode his veto.  Although he encouraged the prosecution of the alleged perpetrators of the Star Route scandal, their acquittal by juries undercut the president’s popularity.  His administration continued the modernization of the U.S. Navy begun during Garfield’s brief tenure. 

Unbeknownst to the public, Arthur suffered from Bright’s Disease, a usually fatal kidney ailment, with symptoms of episodic nausea, mental depression, and lethargy.  He denied rumors of illness that surfaced occasionally in the press.  In 1884, the Republican Party selected James G. Blaine as its presidential nominee over Arthur.  By his presidential policies, Arthur had alienated conservatives without gaining the trust and support of the reformers.  After leaving office in March 1885, Arthur's health declined rapidly, and he died of a cerebral hemorrhage in November 1886.  Concerned about his reputation, he destroyed all his personal papers and records before he died.