TAMA, IOWA - JUNE 01: Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, travels through the countryside during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 near Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, stops in the city's downtown during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: People gather along the railroad tracks to watch as Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, makes a stop in the city's downtown during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: People gather along the railroad tracks to watch as Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, makes a stop in the city's downtown during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: People gather along the railroad tracks to watch as Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, arrives in town during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Belle Plaine, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: People gather along the railroad tracks to watch as Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, makes a stop in the city's downtown during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, travels through the countryside during its cross-country journey to celebrate America's 250th birthday on June 1, 2026 near Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)

TAMA, IOWA - JUNE 01: People gather along the railroad tracks to watch as Union Pacific’s Big Boy No. 4014, the world’s largest operating steam locomotive, departs the city's downtown on its cross-country journey to celebrate America's 250th birthday on June 1, 2026 in Tama, Iowa. Between 1941 and 1944 Union Pacific commissioned 25 Big Boy locomotives, eight still remain, but the restored 4014 is the only one that is fully operational. (Photo by Scott Olson/Getty Images)