Sorry, I couldn't find pricing data for that day. The closing price for the S&P 500 (GSPC) on January 18, 2019 was $2,670.71. It was up 0.7% for the day. The latest price is $6,552.51.
DATE
OPEN
HIGH
LOW
CLOSE
VOLUME
January 18 2019
$2,651.27
$2,675.47
$2,647.58
$2,670.71
4,009,010,000
Daily pricing data for the S&P 500 dates back to 12/30/1927, and may be incomplete.