What are broad shoulders?

This made me curious as i'm the same height, mine are 37 diameter and 16 in width

You're more likely to have them if you're from Chicago.

Hog Butcher for the World,
Tool Maker, Stacker of Wheat,
Player with Railroads and the Nation's Freight Handler;
Stormy, husky, brawling,
City of the Big Shoulders:

They tell me you are wicked and I believe them, for I
have seen your painted women under the gas lamps
luring the farm boys.
And they tell me you are crooked and I answer: Yes, it
is true I have seen the gunman kill and go free to
kill again.
And they tell me you are brutal and my reply is: On the
faces of women and children I have seen the marks
of wanton hunger.
And having answered so I turn once more to those who
sneer at this my city, and I give them back the sneer
and say to them:
Come and show me another city with lifted head singing
so proud to be alive and coarse and strong and cunning.
Flinging magnetic curses amid the toil of piling job on
job, here is a tall bold slugger set vivid against the
little soft cities;

Fierce as a dog with tongue lapping for action, cunning
as a savage pitted against the wilderness,
Bareheaded,
Shoveling,
Wrecking,
Planning,
Building, breaking, rebuilding,
Under the smoke, dust all over his mouth, laughing with
white teeth,
Under the terrible burden of destiny laughing as a young
man laughs,
Laughing even as an ignorant fighter laughs who has
never lost a battle,
Bragging and laughing that under his wrist is the pulse.
and under his ribs the heart of the people,
Laughing!
Laughing the stormy, husky, brawling laughter of
Youth, half-naked, sweating, proud to be Hog
Butcher, Tool Maker, Stacker of Wheat, Player with
Railroads and Freight Handler to the Nation.