The Jim Henson Foundation was founded by puppeteer and Muppet creator Jim Henson to promote and develop puppetry in the United States.
 Jim Henson's daughter Cheryl Henson currently serves as the president for the Foundation.
Don Sahlin (June 19, 1928 in Stratford, Connecticut – February 19, 1978 in New York City) was a Muppet designer and builder who worked for Jim Henson from 1962 to 1977.
 His first creation for Jim Henson was Rowlf the Dog, which he built in 1962 for a series of Purina Dog Chow commercials.
 Don would go on to design and build most of the Muppet characters, including Bert and Ernie, Grover, and Cookie Monster among others.
 His character designs are often recognizable for their spheroid heads partially bisected to create large mouths.
 Although always based on sketches by Jim Henson, the Muppet founder regularly stated that it was Don who should be credited with creating the actual Muppet "look", and Henson later had a bench in London dedicated to his memory.
 The series finale of "Fraggle Rock" is also dedicated to him.
 After all the regular credits have been shown, a special credit appears which reads "This show is for Don Sahlin".
James Maury "Jim" Henson (September 24, 1936 – May 16, 1990) was an American puppeteer, artist, cartoonist, inventor, screenwriter, and filmmaker who achieved international fame as the creator of the Muppets.
 Born in Greenville, Mississippi, and raised in Leland, Mississippi, and Hyattsville, Maryland, Henson began developing puppets while attending high school.
 While he was a freshman at the University of Maryland, College Park, he created "Sam and Friends", a five-minute sketch-comedy puppet show that appeared on television.
 After graduating from the University of Maryland with a degree in home economics, he produced coffee advertisements and developed some experimental films.
 Henson founded Muppets Inc. in 1958 (which would later become the Jim Henson Company).
Jim Henson's Pajanimals (a portmanteau of the words "Pajamas" and "Animals") is a children's TV series created by Jeff Muncy.
 It airs on Sprout in the United States and Nick Jr. in the United Kingdom.
 The Pajanimals are characters that were made by Jim Henson's Creature Shop at The Jim Henson Company.
Jim Henson Pictures is an American film studio, owned by The Jim Henson Company and operated by Brian and Lisa Henson.
 It was founded on July 21, 1995, as a joint venture between Jim Henson Productions and Sony Pictures Entertainment.
 However, the company's films suffered from poor box office performances, which led to Sony breaking from the joint venture after the release of "The Adventures of Elmo in Grouchland"; further films were released under the name of The Jim Henson Company, although they were credited under their former name on "Good Boy!
" in 2003.
Heather Beth Henson (born December 19, 1970, in New York City) is a contemporary puppet artist.
 She serves on The Jim Henson Company, The Jim Henson Legacy, and the Jim Henson Foundation Boards of Directors.
 She is also a Trustee of the Eugene O'Neill Theater Center in Connecticut.
Fraggle Rock (also known as Jim Henson's Fraggle Rock or Fraggle Rock with Jim Henson's Muppets) is a British/American/Canadian children's live action puppet television series about interconnected societies of Muppet creatures, created by Jim Henson.
Jim Henson Television is the television production arm of The Jim Henson Company.
 Jim Henson Television has developed many creative shows over the span of four decades.
Shirley Clarke (October 2, 1919 – September 23, 1997) was an American experimental and independent filmmaker.
 She was also a director and editor to many famous works.
The Jim Henson Company (also known at various times as Muppets, Inc., Henson Associates, Inc., and Jim Henson Productions, Inc.) is an American entertainment company, a leading producer of children's and family entertainment (despite some of the company's works containing mature content), and best known as the creators of the renowned Muppets characters.
 Founded in 1958 by puppeteer Jim Henson and performing partner and wife Jane Henson, the company is independently owned and operated by the children of its founders.

Question: Were both Shirley Clarke and Jim Henson American?
Answer: yes