He was privately tutored as a youth, and also attended Baltimore City College and Deichmann Gymnasium School.
[1] In 1904, Marbury was admitted to the Maryland Bar and entered into private practice in Prince George's County and Baltimore.
[1] From 1910 to 1912, Marbury served as a member of the Maryland House of Delegates, representing Prince George's County.
[1][2] In the House, he was chairman of the Ways and Means Committee in 1912, and also as Democratic Floor Leader that same year.
He was an at-large delegate to the 1920 Democratic National Convention, and chairman of the Maryland State Board of Prison Control from 1920 to 1923.