This move led to his being hired in 1859 as the first director of Harvard College's new gymnasium, where he worked for fourteen years, serving as an instructor in gymnastics, baseball, rowing, and boxing, coaching sports teams, and managing the gym's equipment.

[6] Aaron Hewlett was active in the fight for civil rights for African Americans in Massachusetts, challenging illegal discrimination in public places and supporting alternatives to discriminatory institutions.

[8] Two years later he was part of a group of twenty people who petitioned to have the license of a Cambridge skating rink revoked on grounds of unlawful discrimination.

Also in 1868, he was part of a group that incorporated the Cambridge Land and Building Association, an organization formed to provide loans for African Americans who could not get service from white-run banks.

[15] As a member of the Supreme Court bar, Hewlett was involved in ten cases as counsel or co-counsel, often joining appeals filed on behalf of black southern defendants.

Whipper in a case that made similar arguments, again seeking to overturn a murder conviction on the grounds that black jurors had been excluded due to their race or color.

In this case, the court concluded that Hewlett and his colleagues had failed to prove that blacks were purposefully excluded from juries by the administration of the law.

This has been interpreted as a victory for the idea that black defendants were entitled to a jury that included their black peers, making Smith the first African American attorney to successfully argue a case before the Supreme Court; however, the court's decision was narrowly focused on procedure, specifically the fact that Carter had never been given a chance to object to the composition of the grand jury (which had been empaneled before charges were filed against him), in violation of Texas law.

[16] He also pushed back against denial of service in 1907 by alerting the federal marshall in charge of the District of Columbia city hall that a lunchroom in the building had refused to serve him and a black colleague.

Although the marshall, who had given the lunchroom operator free use of the space, informed her that discrimination was illegal, she responded by closing the restaurant on the grounds that her white patrons would not share a facility with blacks.

In 1902, he officiated at the wedding of Julia Johnson and George Wilson from Baltimore, who came to Washington and were married in his court because their home state of Maryland prohibited interracial marriage.

White-run companies were often unwilling to conduct real estate transactions or sell insurance to black customers, who they believed were inherently bad risks, so these ventures provided a needed alternative.

[41] He belonged to civil rights groups that emerged at the turn of the twentieth century to support the enforcement of the Thirteenth, Fourteenth and Fifteenth amendments and to fight against discrimination, segregation and the Jim Crow legal system, and lynching.

[43] During the 1910s and 1920s he was actively involved in the National Equal Rights League,[44] and during World War I he participated in protests in Washington, DC against mistreatment of African American soldiers.