NEW YORK — Early-bird shoppers headed to stores on Thanksgiving in what’s becoming a new holiday tradition.

In the Chicago suburb of Naperville, Ill., the parking lot of a Walmart store was full roughly 30 minutes before Thanksgiving deals started at 6 p.m., including $199 iPad minis.

In New York City, there were 500 people in line by the time a Target store in the East Harlem neighborhood opened at 6 p.m.

And 200 people rushed in at the Toys R Us in New York City’s Times Square when it opened at 5 p.m.

Mary Smalls, 40, was out trying to get all her shopping done on Thanksgiving because she wanted to avoid going out on the day after the holiday that’s known as Black Friday.

“I’m going to try to avoid the crowds,” said Smalls, who plans to spend $300 to $400 on gifts this year.

Thanksgiving shopping has come a long way. Just a few years ago when a few stores started opened late on the holiday, the move was met with resistance from workers and shoppers who believed the day should be sacred.

But last year, more than dozen major retailers opened at some point on Thanksgiving evening. And this year, at least half of them — including Target, Macy’s, Staples and J.C. Penney — opened earlier in the evening on the holiday.

The Thanksgiving openings are one way retailers are trying to compete for Americans’ holiday dollars. Used to be that Black Friday was when they’d focus their sales promotions. But increasingly, they’ve been pushing those promotions earlier on Friday — and eventually into the holiday itself — to grab deal-hungry shoppers’ attention.

Bill Martin, co-founder of ShopperTrak, which tracks data at 70,000 stores globally, is expecting a sales increase of 3 percent to 5 percent to $2.57 billion to $2.62 billion on Thanksgiving. Last year’s figure grew two-fold from the year before.

The National Retail Federation expects 25.6 million shoppers to take advantage of the Thanksgiving openings, down slightly from last year.

Kathy Grannis, a spokesman at the retail trade group, said earlier promotions in the month and shoppers’ uncertainty about when they can get the best deals are factors that could lead to fewer shoppers coming out on the holiday.

Nevertheless, Thanksgiving is starting to take a bite out of Black Friday business. Indeed, sales dropped 13.2 percent to $9.74 billion on Black Friday last year. Analysts said Thanksgiving sales were in part responsible for the decline.

And Gerald Storch, who runs a retail consultancy called Storch Advisors, said stores that open on Thanksgiving get more of their share of sales for the four-day holiday weekend than others who open on Friday.