[1] After receiving a Master of Journalism degree in 1948, Matthiesen was appointed editor of the diocesan newspaper The West Texas Catholic.
In 1961. he received a Master of School Administration degree and in 1962 was appointed rector of St. Lucian's Preparatory Seminary in Amarillo.
Matthiesen was awarded a Doctor of Journalism degree in 1961, and in 1968 was named principal of Alamo Catholic High School.
''[3]In 1992, Matthiessen called for a stay of execution for Johnny Frank Garrett, a Texas man convicted of raping and murdering 76 year-old Sister Tadea Benz at an Amarillo convent.
[4] Matthiesen admitted eight priests into the Diocese of Amarillo after they had undergone treatment following accusations of sexual impropriety.
[5] His most controversial priest assignments are Orville Blum, Mattheisen appointed as Principal of Alamo Catholic High and pastor of Sacred Heart Church in Amarillo.
[8] Also in 2004, Matthiessen stirred controversy when he started a fundraising effort to assist three priests whom his successor bishop had removed from public ministry.