“Cass Timberlane” is a romantic drama film starring Spencer Tracy, Lana Turner and Zachary Scott, directed by George Sidney, and released in 1947. It was based on the 1945 novel Cass Timberlane: A Novel of Husbands and Wives by Sinclair Lewis, which was Lewis’ nineteenth novel and one of his last.
Former Congressman and now Judge Cass Timberlane is a middle-aged, incorruptible, highly respected man who enjoys good books and playing the flute. He falls for Jinny (Lana Turner), a much younger girl from a lower class in his small Minnesota town.
At first, the marriage is happy, but Jinny becomes bored with the small town and with the judge’s friends.
She leaves him for an affair with a lawyer, Timberlane’s boyhood friend.
Eventually abandoned by her lover, Jinny returns to her husband and becomes the good wife.
The novel is Lewis’ examination of marriage, love, romance, heartache and trust.

Lana Turner plays Virginia “Jinny” Marsland.

From Variety: “Miss Turner is the surprise of the picture via her top performance. In a role that allows her the gamut from tomboy to the pangs of childbirth and from being another man’s woman to remorseful wife, she seldom fails to acquit herself creditably. 
In the New York Daily News, Kate Cameron wrote: “There is no doubt about it, Lana Turner screens more beautifully than any other blonde in Hollywood. In “Cass Timberlane”, she literally illumines the Music Hall screen with a glow that is soft, warm and altogether feminine. That she is able to hold the spotlight while Spencer Tracy is on the scene is a test of her ability as an actress and a charmer. Her vis-a-vis in the picture is a veteran of screen and stage who knows how to command attention when he wishes. He is always sure of himself, even when he gives way a bit to let the glamourous Lana have the spotlight.

Lana was happy to work with Spencer Tracy again and to be playing a complex part in a contemporary setting. She got to experiment with hairstyles again. It was cropped short and lightened up from “Green Dolphin Street.” She was given several lovely costumes, but she also had fun letting the tomboy in her come out by donning a baseball cap, blue jeans and loafers and getting dirty sliding into a home plate during a game of baseball.

Trailer:

You can watch the film here.

Lana Turner did a lot of movies. She really loved being a moviestar.
Here are the most important films in which she starred. Just click the links for more info, photos and videos.

20 April 1937: A Star Is Born
9 Oct. 1937: They Won’t Forget
24 Oct. 1937: The Great Garrick
1 Jan. 1938: The Adventures of Marco Polo
22 July 1938: Love Finds Andy Hardy
12 Aug. 1938: Rich Man, Poor Girl
9 Dec. 1938: Dramatic School
28 April 1939: Calling Dr. Kildare
18 Aug. 1939: These Glamour Girls
29 Sept. 1939: Dancing Co-Ed
19 April 1940: Two Girls on Broadway
19 July 1940: We Who Are Young
25 April 1941: Ziegfeld Girl
12 Aug. 1941: Dr. Jekyll and Mr. Hyde
2 Oct. 1941: Honky Tonk
18 Febr. 1942: Johnny Eager
27 Aug. 1942: Somewhere I’ll Find You
1 April 1943: Slightly Dangerous
19 Aug. 1943: Du Barry Was A Lady
13 Nov. 1943: The Youngest Profession
23 Aug. 1944: Marriage Is a Private Affair
8 March 1945: Keep Your Powder Dry
1 Oct. 1945: Week-End At The Waldorf
2 May 1946: The Postman Always Rings Twice
5 Nov. 1947 : Green Dolphin Street
1 Nov. 1947: Cass Timberlane
29 April 1948: Homecoming
20 Oct. 1948: The Three Musketeers
1 Sept. 1950: A Life Of Her Own
2 March 1951: Mr. Imperium
5 Sept. 1952: The Merry Widow
25 Dec. 1952: The Bad And The Beautiful
25 Aug. 1953: Latin Lovers
1 May 1954: Flame And The Flesh
7 Sept. 1954: Betrayed
13 May 1955: The Prodigal
4 June 1955: Sea Chase
14 Dec. 1955: The Rains Of Ranchipur
12 Jan. 1956: Diane
13 Dec. 1957: Peyton Place
30 Jan. 1958: The Lady Takes A Flyer
2 May 1958: Another Time, Another Place
30 April 1959: Imitation Of Life
23 June 1960: Portrait In Black
19 July 1961: By Love Possessed
2 Nov. 1961: Bachelor In Paradise
25 Dec. 1962: Who’s Got The Action?
24 Febr. 1965: Love Has Many Faces
27 April 1966: Madame X
30 April 1969: The Big Cube
7 Nov. 1974: Persecution
27 Oct. 1976: Bittersweet Love
31 Oct. 1980: Witches Brew
21 May 1982: Dead Men Don’t Wear Plaid

Sources: Wikipedia, IMDB, Rotten Tomatoes, Lana’s biography “Lana, the Lady, The Legend, The Truth“, “The Films Of Lana Turner” by Lou Valentino and “Lana Turner, The Memories, The Myths and The Movies” by Cheryl Crane.