If you are not certain how to differentiate between a fashion boutique and a clothing store, don't worry.  Not many people do understand the difference (if their is one).  From the links below, you will find clothing stores and clothing store directories.  Hopefully, this will help you find retailers that are offering designer fashion.

Clothing Stores - directory
Apparel Retailer - search engine

Neiman Marcus
Bloomingdales
Bergdorf Goodman
Lord & Taylor
Nordstrom
Dillard's
Belk
Gap
Express
Wet Seal

Sure, their are many more clothing stores.  However, we could not list them all on this page.  If you are interested in find more apparel retailers, you can use the ApparelRetailer.com search engine.  That engine will search the internet.
 

Designer Fashion Boutique Guide

Fashion Boutique Directories
Fashion Designers
Fashion Designer Outlets
Luxury Fashion Brands
Local Deals
Shopping Clubs
Clothing Stores
Boutiques.com