There's a reason why "Thanks, Penneys!" is one of the most uttered phrases in Ireland.

Primark, operating as Penneys in Ireland, is officially the fastest-growing retailer in America.

The National Retail Federation’s Stores magazine published data that proves that the affordable apparel and homeware chain is one to watch.

Primark has opened nine stores in the US since 2015 - with plans to keep expanding. According to Kantar Consulting, the store’s US sales are up an incredible 103% this year, after the opening of further stores in areas like Brooklyn.

The colossal Brooklyn store boasts 56 fitting rooms and 42 checkout lanes: much to the delight of New York's massive community of Irish expats.

Read More: Thanks, Penneys! Beloved Irish fashion chain opening in Brooklyn

Primark, which opened its first store in Dublin in 1969, will be expanding to New Jersey and Florida next year. The retailer cannot operate under the name Penneys outside of Ireland due to confusion with established giant, JCPenney. 

The brand recently announced that it was to expand on its existing size offerings.

The popular store will now offer S, M, L instead of numbered sizing, and take its size range from 2XS (a US size 0/UK size 4) to 2XL (a US size 20/UK size 24).

"We have updated our sizing for a more comfortable fit - we will be grouping sizes into S/M/L etc, rather than 8/10/12, etc.," a representative from the company said.

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