BOSTON (AP) — Thousands of competitors and spectators are in Boston for the Head of the Charles regatta, an event that organizers expect to generate at least $54 million to the Massachusetts economy in one weekend.

Read: Your guide to the Head of the Charles

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The two-day rowing competition began Saturday morning and will end on Sunday evening. Organizers say the event is expected to attract nearly 11,000 athletes from 32 countries, together with more than 400,000 spectators.

The 50th annual event takes place on a three-mile course in the Charles River between Cambridge and Boston.

Related: Complete Head of the Charles coverage

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Competitors in the regatta race against the clock, leaving the starting line in single file, approximately 15 seconds apart.

The race attracts youth, collegiate, masters, international, world champion and Olympic athletes participating in 61 events.

Organizers say the regatta has generated at least $1 billion to the local economy in 50 years.

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