What is Chester Arthur's legacy?

Chester Arthur was the Twenty-First President of the United States. His term began when president Garfield was assassinated in 1881. Many in the Republican Party believed that when Arthur assumed the office, he was not well-prepared for or capable of serving as President. Arthur had long been associated with the political machine of Roscoe Conkling, a Senator who controlled what was known as the Stalwart Republican Machine. It was assumed with Chester Arthur as President the politics characterized by political patronage and favoritism would continue unabated.
In the election of 1880, the machine supported the renomination of President Grant. When Grant's nomination faltered, Conkling and his supporters put their efforts behind Arthur to be nominated for Vice President of the United States. Conkling's group wanted to continue the machine politics which relied heavily on political patronage. Believing Chester Arthur was one of their own, Conkling's group was confident Arthur would not do anything to disrupt machine politics and political patronage. The untimely assassination of Garfield elevated Arther to the presidency and to the dismay of Conkling, the once reliable Arthur turned against them.
To the shock of Conkling and the Stalwart Republican Machine, Chester Arthur as President pursued civil service reforms which undercut the power of the political machine. Congress with Arthur's support passed the Pendleton Act in 1883. The Pendleton Act created a Civil Service Commission to oversee federal government employment assuring applicants fair treatment in obtaining civil service jobs and more importantly, prohibiting certain government employees from being fired for political reasons. The act reduced the influence of machine politics by taking their primary source of patronage from them, employment in a government job.
Reform of government employment practices and openly rejecting the machine patronage system of the day may be Arthur's most significant legacy. In the short time he held office Chester Arthur supported the first attempt at general immigration law and reform. He supported lower tariffs and signed the Tariff Act of 1883. It is fair to characterize Chester Arthur's presidency as mundane in most areas except civil service reform which was a bold reform at the time.
https://millercenter.org/president/arthur

https://www.history.com/topics/us-presidents/chester-a-arthur

https://www.whitehouse.gov/about-the-white-house/presidents/chester-a-arthur/