* American Express boosts Dow after results
* Investors eye first round of French election this Sunday
* Dow up 0.85 pct, S&P 500 up 0.76 pct, Nasdaq up 0.92 pct (Updates to market close)
By Chuck Mikolajczak
NEW YORK, April 20 (Reuters) - U.S. stocks rallied on Thursday, with the Nasdaq closing at a record, as a round of solid earnings led by American Express pushed equities higher.
The credit card company closed up 5.9 percent as the top boost to the Dow Industrials after reporting a smaller-than-expected drop in quarterly profit late Wednesday.
CSX Corp, up 5.6 percent, was one of the best performers on the S&P 500 after the railroad reported a better-than-expected quarterly net profit driven by rising freight volumes and said it plans to cut costs and boost profitability moving forward.
"You need a catalyst to go higher and the only one that is out there to me that is logical and would drive the market higher is earnings, and so far it is OK," said Phil Blancato, CEO of Ladenberg Thalmann Asset Management in New York.
"You look at a day like today and it tells you there is a lot of cash on the sidelines that wants an opportunity to buy when the market sells off even just a little bit."
Major indexes have fallen for two straight weeks, retreating from record levels as worries about President Donald Trump's ability to deliver on his pro-growth promises raised some concern about stretched stock valuations.
Mounting tensions between North Korea and the United States, as well as the looming French presidential elections, also served to heighten investor caution. Recent polls showed centrist Emmanuel Macron hung on to his lead in a four-way French race that is too close to call.
Of the 82 companies in the S&P 500 that have reported earnings through Thursday afternoon, about 75 percent have topped expectations, according to Thomson Reuters data, above the 71 percent average for the past four quarters.
Overall, profits of S&P 500 companies are estimated to have risen 11.1 percent in the quarter, the best since 2011.
The Dow Jones Industrial Average rose 174.22 points, or 0.85 percent, to 20,578.71, the S&P 500 gained 17.67 points, or 0.76 percent, to 2,355.84 and the Nasdaq Composite added 53.74 points, or 0.92 percent, to 5,916.78.
The S&P 500 closed just below its 50-day moving average, a level that had acted as resistance after the index fell below it last week.
Philip Morris fell 3.5 percent to $109.98 as the biggest drag to the benchmark S&P index after the tobacco maker's first-quarter profit forecast fell below estimates.
Advancing issues outnumbered declining ones on the NYSE by a 2.49-to-1 ratio; on Nasdaq, a 2.61-to-1 ratio favored advancers.
The S&P 500 posted 40 new 52-week highs and 1 new low; the Nasdaq Composite recorded 117 new highs and 35 new lows.
About 6.65 billion shares changed hands in U.S. exchanges, compared with the 6.3 billion daily average over the last 20 sessions. (Reporting by Chuck Mikolajczak; Editing by Nick Zieminski)