Missouri's coronavirus guidelines say venues must adhere to social distancing measures by placing tables six feet apart and removing all communal seating areas.
Backwater Jacks Bar and Grill hosted the event, the 'Zero Ducks Given Pool Party', and assured guests they would take "extra precautions and safety measures" to prevent the spread of COVID-19.
One guest said while the venue made hand sanitiser available for guests, social distancing was impossible.
"When we walked up my first words were 'oh my gosh' - it was intense for sure! Social distancing was nonexistent. However everyone was enjoying themselves," Jodi Atkins told CNN.
The Memorial Day weekend that signals the start of the US summer is normally a time when cemeteries across the nation fill with American flags and ceremonies to remember those who died in wars.
This year the, holiday week is when the US death from COVID-19 is expected to exceed 100,000.
The New York Times filled its entire front page with the names and selected details of 1,000 victims on Sunday to try to capture the humanity of the lives lost.
"We were trying to capture that personal toll," Marc Lacey, the newspaper's national editor, said.
"We were trying to humanise these numbers which keep growing and have reached such unfathomable heights that they're really hard to grasp any more... This is about everyday people. It's about a death toll, reaching a number that's really just jaw-dropping."
Around the country, the long weekend saw people sunbathing on beaches, fishing from boats and strolling on boardwalks, with the occasional person sporting a mask sometimes the only reminder that the world is still battling the coronavirus pandemic.
Few people wore masks on Saturday while walking on a crowded boardwalk in Ocean City, Maryland.
Source: Sipa USA Paul Hennessy / SOPA Images/Sipa
Masks were also a rare sight on other beaches, but people mainly kept their distance in small groups and avoided playing games like Frisbee and volleyball.
"Personally, I'm not sure I'm worried about that, but for those who are worried ... I suggest they stay home. I like to get out," said Bruce Clark at Daytona Beach in Florida.
With additional reporting from Reuters.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
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