In the 1870s, his parents Nathan (Naphtali) Lowenthal and Gertrude (Nahamah) Gitel, both Orthodox Jewish, emigrated from Kovno (now Kaunas), Lithuania, to Minnesota.

He received a BA in 1909 from the University of Minnesota and graduated in 1912 from Harvard Law School, where he began a lifelong friendship with Felix Frankfurter.

On one hand, he has been an assiduous cultivator of high-level friendships, including Presidents Roosevelt and Truman and Supreme Court Justices Felix Frankfurter and Louis Brandeis.

Alger Hiss and Lee Pressman benefited by his friendship, and, for a time, did one George Shaw Wheeler, a young lawyer who became so carried away by communism that he denounced his United States citizenship to make a new career bebind the Iron Curtain.

[20] Another important protege of Lowenthal's (and his partner Robert Szold) was Benjamin V. Cohen, later known as one of Felix Frankfurter's Hotdogs in the New Deal.

It lists chairman Hyman Blumberg, president R. L. Redheffer, vice president Jacob S. Potofsky, cashier Leroy Peterson, and other directors: Hillman, August Bellanca, Joseph Gold, Fiorello H. La Guardia, Abraham Miller, Joseph Schlossberg, Murray Weinstein, Max Zaritzky, and Peter Monat.

While making the rounds "as agents of the President" with Tommy Corcoran (one of Felix Frankfurter's "Happy Hotdogs"), Lowenthal told any and all that nothing would happen "without the help of railway labor.

Senators on that subcommittee included: Wheeler (chair), Truman, Alben Barkley, Victor Donahey, Wallace White, and Henrik Shipstead.

Lowenthal went with Truman to meet with Philip Murray, head of the Congress of Industrial Organizations (CIO) union federation, for support.

[37][38][39][40][41][42][43] In 1950, Lowenthal published a book critical of the Federal Bureau of Investigation (see Works, below), which led to him being called before the House Un-American Activities Committee, where he denied he had "aided and abetted" Communist in government service .

[44] On September 15, 1950, Lowenthal appeared before the House Un-American Activities Committee AKA "HUAC" (two of whose members were Mundt and Nixon–of the Mundt-Nixon Bill).

Already in August 1950, HUAC had re-subpoenaed four witness who had been part of Whittaker Chambers's Ware Group: Lee Pressman, Nathan Witt, Charles Kramer and John Abt.

After reviewing his curriculum vitae, the committee tried to link him with known or alleged Communist Party members and organizations, some of which he confirmed, others not, all without admitting any wrongdoing.

Specifically, he denied any involvement in the employment or sponsoring of George Shaw Wheeler, a former US government employee who had defected to Czechoslovakia in 1947 and publicly requested political asylum there in 1950.

Hickenlooper stated "I have the greatest admiration and respect for the integrity of the director, Mr. J. Edgar Hoover, and his staff personnel" at the FBI.

Lowenthal was later unable to recall clearly the names of anyone who helped him: Truman Library oral historian Jerry N. Hess suggested that they might have included Herbert N. Maletz, Lowell Mellett, and Franklin N. Parks.

"[33]) In mid-summer 1951, Truman wrote Lowenthal to thank him for a letter and respond regarding Senator Joseph McCarthy's speech of Jun 14, 1951, attacking George Marshall.

In 1952, when Truman announced he would not seek re-election, Vice President Alben Barkley could not secure the presidential nomination from the Democratic Party due to a lack of endorsement from labor leaders.

So then they made a strategic mistake, because labor leaders are all prima donnas, and I suggested to Les that Barkley set up a meeting with these fellows and talk to them individually.

[1] In 1953, Lowenthal was "member" of the Truman Administration, according to the papers of American evangelist Billy James Hargis (who also lists him among "Alleged Reds" 1950–1954).

[48] Lowenthal's best known accomplishment occurred during his term as the chief adviser on Palestine to Clark Clifford, an advisor to President Truman, from 1947-1952.

[citation needed] President Truman credited Lowenthal as being the primary force behind the United States recognition of Israel.

[21] In the late 1950s, Norman Thomas criticized Bertrand Russell for citing Lowenthal and Cedric Belfrage as authorities on wrongdoings by the FBI.

[50] As late as 1967, Lowenthal denied ever even discussing Israel with President Truman and claimed to have only heard of the partition of Palestine through a secondhand source in the White House.

[57] Spingarn further recalled: There was an operation run, more or less, under the supervision of Max Lowenthal in the basement of the White House which was to prepare answers to the charges that McCarthy was hurling so freely during all that period and get them ready in a hurry, not wait until the lie had gone around the world before the truth has gotten its pants on.

[58]After the FBI book came out, Westbrook Pegler, a right‐wing columnist, called Lowenthal "the mysterious New York lawyer, who now appears to have picked Harry Truman for President.

[59] In the inaugural issue of the Monthly Bulletin of the International Juridical Association (May 1932), "Max Lowenthal, member of the New York bar" appears in an article called "Protest Meeting.

The New York Times announced the book a day in advance of its publication on November 21, 1947, with a subtitle that read "Lawyer Says Hoover Policies Set Up Secret Police.

If Mr. Lowenthal is still looking for evidence as to what can be done through the FBI, under its present centralized direction from Washington, to oppress dissenting individuals and groups, it would be well for him to study the period from December 8, 1941 to the end of 1945.

[65] George M. Elsey, Administrative Assistant to the President (1949–1951) felt that "Lowenthal had a passionate dislike of the FBI and J. Edgar Hoover in particular."