A terrific in-depth obituary in The Washington Post.
David Thomson had this to say about Widmark in his awesome The New Biographical Dictionary of Film:
Widmark came into movies a little later than most male stars, already in his early thirties. But that debut is still haunting, no matter that Widmark was later turned into an authentic hero, suntanned, laconic, and grudgingly aligning himself with proper causes.
Educated at Lake Forest College, he worked there as a teacher, and as a stage and radio actor, befor being cast as Tommy Udo in Kiss of Death (47, Henry Hathaway). The sadism of that character, the fearful laugh, the skull showing through drawn skin, and the surely conscious evocation of a concentration camp degenerate established Widmark as the most frightening person on the screen. The glee in the performance may even have shocked Widmark himself. It made Kiss of Death untypical of Fox or Hathaway. The studio kept him on a leash, and mixed more conventional heavies with nerve-strained heroes, as if to imply that Tommy Udo was the result of overwork: as the spoiled-child owner of Road House (48, Jean Negulesco); the gangster in The Street With No Name (48, William Keighley); menacing Gregory Peck in Yellow Sky (48, William Wellman); a boy’s best friend in Down To The Sea in Ships (49, Hathaway); Slattery’s Hurricane (49, Andre de Toth); as a whining coward hounded by the London underworld in Night and the City (40, Jules Dassin); as the doctor racing against time and bubonic plague in Panic In the Streets (50, Elia Kazan); as a hardnosed, bigoted cop in No Way Out (50, Joseph L. Mankiewicz).
But even as a hero, Widmark barely suppressed malice, anxiety and violence; the straight voice readily broke into a sneer or a giggle; and the eyes once had an insolent way of staring a woman out. That was how he lifted microfilm from Jean Peters’s handbag at the beginning of Pickup On South Street (53, Samuel Fuller). He was excellent as Fuller’s sentimental hoodlum and brought a special relish to the brutal love scenes and to the situation of a guttersnipe able to crow to the police.
Elia Kazan said in regards to Widmark and Panic In the Streets:
I had a great cast. It was a treat in itself just to have Zero Mostel around. I had Jack Palance, making his first picture. And I had Richard Widmark, who was a jewel, as nice a guy as there was in the world. Barbara Bel Geddes played his wife. I cast like a man should. I handpicked everybody just because I liked them …
Panic in the Streets is the first picture I made that I liked. I don’t think you’re aware those people are actors, even Widmark had played nothing but heavies before that. He became famous in Kiss of Death, in which he pushed an old lady in a wheelchair down the stairs, and he had that wonderfully phony, lunatic laugh. We’d worked in the theater together about four or five years earlier, and I returned him to playing a leading man. He had sort of a minor-league charm. But it was a genuine charm. Almost everything he said was amusing and self-deprecatory, and to me, that self-deprecatory attitude is an essential American quality.
I love his face.