From Ancestry.ca
Border Crossing Port Huron Michigan
24 Jan 1915
Stahl, Gertrude, 21, female, single, clerk, last residence: Waterloo; father: Samuel of Waterloo Canada, going to Chicago Illinois.
Doesn't say if she is going for a visit or for work.
She is not with her parents on 1921 census Waterloo.
She is not on any US census in 1921.
Did not find a marriage for her.
There is another Gertrude Stahl b 1893 b USA living in Waterloo but her parents are Edward and Bertha.
Emma Sophia Stahl, 27, b Waterloo, living Toronto, d/o Samuel Stahl & Mary Hamel, married George William Robinson, 31, living Markham, widower, s/o George Robinson & Jane Williamson, 28 Feb 1912, Toronto.
Witn: Clara Stahl and John Richardson both of Toronto.jhb
1921 census Whitechurch Tsp York North
Lot 88 Concession 1
ROBINSON
William, 41, Ontario, farmer
Emma, 37, Ont
Carson, 7, Ont
Joseph Judd, 28, servant.
1921 census Waterloo
REJEFSKEY
Leo, 26, Ont, parents b Germany, labourer
Vera, 21, Ont, parents b Ont
Craigton, 3
Corinne, 11/12
They are living next door to Samuel and Elizabeth Stahl.
On 1911 census the entry is for a Gertrude V
A Gertrude Violet Stahl is buried Mt Hope Waterloo Reference WA-4500.
You will have to contact the cemetery for more information.
http://ocfa.islandnet.com/ocfa-search.php