LOS ANGELES — On the boardwalk of Venice Beach, the trinkets seem endless. There are glass pipes, copper necklaces, feather earrings and painted wooden skulls.

Just east of MacArthur Park, along Alvarado Street in the Westlake neighborhood of Los Angeles, the sidewalk hums with people selling and buying tamales, faux leather wallets, cellphone accessories and perfume.

The two street markets are separated by 15 miles, and are worlds apart. In Venice, there are throngs of tourists, clusters of wandering teenagers and countless signs for medical marijuana. Near Alvarado, the sidewalks are crowded with immigrants hustling to and from work and grandmothers looking for the latest pills to ease their ailments.

But both markets are illicit, says the City of Los Angeles, and officials are beginning to crack down. Illegal vendors, the authorities say, bring with them threats of crime and an influx of people eager to sleep on city streets. Storekeepers who rent space on the other side of the Venice boardwalk complain that they are losing customers to the sidewalk sellers, or losing foot traffic altogether.