Social Reformer, Civil Rights Activist. A former technology manager at IBM, she was the lead plaintiff in the Supreme Court of the United States case United States v. Windsor, which successfully overturned Section 3 of the Defense of Marriage Act and was considered a landmark legal victory for the same-sex marriage movement in the United States. While attending New York University, Windsor worked for the university's math department, entering data into its UNIVAC. She also worked as a programmer at Combustion Engineering, Inc., where she worked with physicists and the UNIVAC. After receiving her master's degree in mathematics in 1957 from New York University, Windsor began work in senior technical and management positions at IBM in 1958. Her work at IBM was primarily related to systems architecture and implementation of operating systems and natural language processors. In May 1968, she attained the title designating the highest level technical position at IBM, Senior Systems Programmer. She received the first IBM PC delivered in New York City. However, the company rejected her insurance form naming Spyer as a beneficiary. In 1975, IBM moved Windsor's group out of the area, and she took a severance package to focus more on her activism. In June 1969, Windsor and Spyer returned from a vacation in Italy to discover the Stonewall Riots had begun the night before. In the following years, the couple publicly participated in LGBT marches and events. They also lent their Cadillac convertible to LGBT rights organizations. Following her departure from IBM in 1975, she increased her involvement with LGBT organizations. She volunteered for the Gay & Lesbian Advocates & Defenders, the East End Gay Organization, the LGBT Community Center, 1994 Gay Games New York, and helped found Old Queers Acting Up, an improv group utilizing skits to address social justice issues. She served on the board of Services & Advocacy for GLBT Elders (SAGE) from 1986 to 1988 and again from 2005 to 2007. Since her involvement with United States v. Windsor, Windsor has spoken publicly many times advocating for same-sex marriage. She helped Senator Dianne Feinstein and Representative Jerrold Nadler introduce the Respect for Marriage Act at a press conference in Washington, D.C. in 2011. Upon Spyer's death on February 5, 2009, Windsor became the executor and sole beneficiary of Spyer's estate, via a revocable trust. Windsor was required to pay $363,053 in federal estate taxes on her inheritance of her wife's estate. Had federal law recognized the validity of their marriage, Windsor would have qualified for an unlimited spousal deduction and paid no federal estate taxes. Windsor sought to claim the federal estate tax exemption for surviving spouses. She was barred from doing so by Section 3 of the Defense of Marriage Act (DOMA) (codified at 1 U.S.C. § 7), which provided that the term "spouse" only applied to marriages between a man and woman. The Internal Revenue Service found that the exemption did not apply to same-sex marriages, denied Windsor's claim, and compelled her to pay $363,053 in estate taxes. On November 9, 2010, Windsor filed a lawsuit against the federal government in the U.S. District Court for the Southern District of New York, seeking a refund because DOMA singled out legally married same-sex couples for "differential treatment compared to other similarly situated couples without justification." On June 6, 2012, Judge Barbara S. Jones ruled that Section 3 of DOMA was unconstitutional under the due process guarantees of the Fifth Amendment and ordered the federal government to issue the tax refund, including interest. The U.S. Second Circuit Court of Appeals affirmed in a 2-1 decision on October 18, 2012. On March 27, 2013, the U.S. Supreme Court heard oral arguments. On June 26, 2013, the U.S. Supreme Court issued a 5–4 decision declaring Section 3 of DOMA to be unconstitutional "as a deprivation of the liberty of the person protected by the Fifth Amendment." Windsor received numerous awards related to her work in technology and LGBT activism.