Walmart launched its grocery pickup service in Maryland Wednesday at three Baltimore-area stores.

The free service is available at stores in Cockeysville, Severn and Aberdeen.

Shoppers can place orders online, choose a day and time for pickup and pull up in front of the store to get items without getting out of their cars.

"Our customers have told us that grocery pick up is a game changer," Harry Anuszewski, manager of the Cockeysville store, said in the company's announcement.

Customers can choose from 30,000 items. Top items at stores that offer the service have been fresh meat, dairy and produce.

Shoppers can order through the retailer's website at walmart.com/grocery or through the Walmart Grocery mobile app, enter a zip code and create a shopping list. Personal shoppers at each store select products and package them for pickup in reserved parking spaces.

By the end of the year, Walmart's online grocery pickup will be available in 100 markets and about 600 stores. The retailer started the service in 2013 in Denver. The discounter plans to add another 500 locations next year.