Question: Of Thee I Sing: A Letter to My Daughters is a children's book by former United States President Barack Obama, the stories of thirteen Americans are told in the book, including Jackie Robinson, who was an American professional baseball second baseman who became the first African American, to play in which organization?
Context: The presidency of Barack Obama began at noon EST on January 20, 2009, when Barack Obama was inaugurated as President of the United States, and ended on January 20, 2017.  Obama, a Democrat, took office as the 44th United States president following a decisive victory over Republican John McCain in the 2008 presidential election.  Four years later, in the 2012 election, he defeated Mitt Romney to win re-election.  He was the first African American president, the first multiracial president, the first non-white president, and the first president to have been born in Hawaii.  Obama was succeeded by Republican Donald Trump, who won the 2016 presidential election. Devaris "Dee" Strange-Gordon (born April 22, 1988) is an American professional baseball second baseman for the Miami Marlins of Major League Baseball (MLB).  He previously played for the Los Angeles Dodgers.  With the Dodgers, Gordon was primarily a shortstop.  In 2015, in his first season with the Marlins, Gordon hit .333 for a total of 205 hits and stole 58 bases.  He led the NL in all three categories and became the first NL player to lead the league in both batting average and stolen bases since fellow second baseman Jackie Robinson in 1949. In Major League Baseball, the Rookie of the Year Award is annually given to one player from each league as voted on by the Baseball Writers' Association of America (BBWAA).  The award was established in 1940 by the Chicago chapter of the BBWAA, which selected an annual winner from 1940 through 1946.  The award became national in 1947; Jackie Robinson, the Brooklyn Dodgers' second baseman, won the inaugural award.  One award was presented for both leagues in 1947 and 1948; since 1949, the honor has been given to one player each in the National and American League.  Originally, the award was known as the J. Louis Comiskey Memorial Award, named after the Chicago White Sox owner of the 1930s.  The award was renamed the Jackie Robinson Award in July 1987, 40 years after Jackie Robinson broke the baseball color line. Of Thee I Sing: A Letter to My Daughters is a children's book by former United States President Barack Obama, with illustrations by Loren Long.  It is described by the publisher as "a moving tribute to thirteen groundbreaking Americans and the ideals that have shaped our nation."  The stories of thirteen Americans are told in the book: George Washington, Abraham Lincoln, Martin Luther King, Neil Armstrong, Sitting Bull, Cesar Chavez, Billie Holiday, Maya Lin, Albert Einstein (who was born in Germany), Georgia O'Keeffe, Jackie Robinson, Helen Keller, and Jane Addams." Shefali Razdan Duggal (born November 22, 1971) is an Indian-born American Democratic political activist in San Francisco who is a Presidential Appointee to President Barack Obama to the United States Holocaust Memorial Council, which supervises the United States Holocaust Memorial Museum, for a term expiring in January 2018.  She was an active fundraiser for the Barack Obama election campaign in 2008 where she was a Trustee for the DNC South Asian American Leadership Council.  She focused on South Asian and Young Professional outreach, co-hosting a number of fundraising events for both the Senator and his surrogates.  She was a member of President Barack Obama's National Finance Committee for his reelection campaign in 2012, a co-chair for Obama Victory Trustees, and the Northern California Finance Committee.  She worked on the Massachusetts Democratic Party, New Hampshire Democratic Party, and Senators Ted Kennedy and Dianne Feinstein.  She also worked on the Al Gore presidential campaign in 2000, and Hillary Clinton’s presidential campaign in 2008. Zeituni Onyango ( ; May 29, 1952 – April 7, 2014) was known as the half-aunt of United States President Barack Obama; she was born into the Luo tribe in Kenya.  Born during the British rule of the Protectorate of Kenya, Onyango was the half-sister of Barack Obama, Sr., father to the president.  The younger Obama refers to her as "Aunti Zeituni" in his 1995 memoir, "Dreams from My Father".  In 2002 she had applied for political asylum in the United States but was denied.  She became notable when her case was leaked in the final days of the 2008 U.S. presidential campaign in which Barack Obama was the Democratic candidate, attracting international media attention. Janice Kaplan is an American novelist, magazine editor, and television producer.  As Editor-in-Chief of "Parade" magazine (2007-2010), the Sunday newspaper supplement with a circulation of 32 million, she was responsible for many important articles, including two cover stories by President Barack Obama.  His first piece, “A Letter To My Daughters,” ran two days before his inauguration and became the basis for his book "Of Thee I Sing: A Letter to My Daughters."  She also published articles by Madeleine K. Albright, Senator John McCain, Justice Sandra Day O'Connor, and Senator Jim Webb.  She wrote cover stories for the magazine on celebrities including Barbra Streisand, Clint Eastwood, Matt Damon and Daniel Craig. Harry Keels Thomas Jr. (born June 3, 1956 in the Harlem section of New York City) is an American diplomat and current United States Ambassador to Zimbabwe.  He served as the United States Ambassador to the Philippines from 2010 to 2013.  A former United States Ambassador to Bangladesh (serving from 2003 to 2005) and Director General of the United States Foreign Service (serving from 2007 to 2009), Thomas was designated by US President Barack Obama on November 19, 2009 to replace Kristie Kenney as Ambassador to the Philippines—the first African American to serve at that post.  He was confirmed by the United States Senate on March 19, 2010 and presented his credentials to Philippine president Gloria Macapagal-Arroyo on April 27, 2010 He was then nominated and confirmed as the United States Ambassador to Zimbabwe on October 22, 2015.  He was sworn in on December 8, 2015. Jack Roosevelt Robinson (January 31, 1919 – October 24, 1972) was an American professional baseball second baseman who became the first African American to play in Major League Baseball (MLB) in the modern era.  Robinson broke the baseball color line when the Brooklyn Dodgers started him at first base on April 15, 1947.  When the Dodgers signed Robinson, they heralded the end of racial segregation in professional baseball that had relegated black players to the Negro leagues since the 1880s.  Robinson was inducted into the Baseball Hall of Fame in 1962. Christopher P. Lu (; born June 12, 1966) is a former United States Deputy Secretary of Labor.  He also served as Assistant to the President and White House Cabinet Secretary for United States President Barack Obama from 2009 to 2013, as well as the co-chair of the White House Initiative on Asian Americans and Pacific Islanders.  Lu graduated from the Woodrow Wilson School at Princeton University and from Harvard Law School, where he was a classmate of Obama's.
Answer: Major League Baseball (MLB)