[1] McWilliams initially followed his parents into the teaching profession but at the age of 20 moved to Hobart and began working as a journalist for the Tasmanian Mail.

[3] In parliament, McWilliams advocated strongly on behalf of farmers, investigated the possibility of introducing sugarbeet farming into Tasmania, and helped found the Tasmanian Meteorological Bureau.

Switching to federal politics, McWilliams won the Franklin at the 1903 election as a Revenue Tariffist supporting the Free Trade Party on most economic issues.

As in state parliament, McWilliams was a staunch advocate on rural matters, supporting the timber industry and primary producers.

After the 1919 federal election, which saw a number of candidates elected with the endorsement of state-based farmers' organisations, McWilliams was one of a five signatories to a letter drafted by William Gibson calling for the formation of a parliamentary Country Party, alongside Henry Gregory, William Hill and Edmund Jowett.

[5] He was elected as the party's inaugural leader on 25 February 1920, with Jowett as his deputy, largely on the basis that he was the only member with prior experience in federal parliament.

[6] In his first parliamentary speech as leader, McWilliams proclaimed that the Country Party would "cursed system of centralization, under which hundreds of thousands of pounds are squandered in our city Departments, whilst necessary adjuncts to civilization, in the way of telephonic communication and mail services are denied to the residents of our back-blocks".

[11] At the 1928 election, McWilliams finally defeated Seabrook as an independent, joining Country Progressive MP Percy Stewart on the crossbench.

[15] McWilliams died suddenly at his home in Battery Point on 22 October 1929, just over a week after his re-election to parliament and on the same day of the declaration of the poll.