Churchill was the last British leader to receive a state funeral, also at St. Paul's. Thatcher's service, a ceremonial funeral with full military honors, is not officially a state funeral, which requires a vote in Parliament.
But the ceremony features the same level of pomp and honor afforded Princess Diana and the Queen Mother Elizabeth.
Thatcher's coffin will lie overnight at the Houses of Parliament ahead of the funeral, before being taken by hearse to the church of St. Clement Danes and then, on a horse-drawn gun carriage, to the 17th-century cathedral along a route lined by military personnel.
The televised funeral will be followed by a private cremation.
Early Tuesday, undertakers removed Thatcher's body from London's Ritz Hotel where she died Monday at the age of 87. A van carrying Thatcher's casket left the hotel for an undisclosed location, where it will remain during preparations for the funeral.
On Monday, Utahn's reacted to the death of Thatcher, who visited the state in 1996:
"A woman who once joked she did know the meaning of defeat, Margaret Thatcher was an unwavering defender of freedom and the British people, and I was honored to get to know her during our service together," said Sen. Orrin Hatch, R-Utah.
"It was a privilege to have known Margaret Thatcher. She exemplified principled and pragmatic leadership which the world is better off for," said former Utah Gov. Jon Huntsman.
"In addition to doing some good things, she also created a tremendous amount of misery and pain for many, many people in Great Britain … she created a great deal of wealth for a lot of corporations and a lot of 1 percenters and she did that on the back of a lot of working people," said Utah Democratic Party Chairman Jim Dabakis.