	(in thousands)
December 31,	2020		2019
Industrial revenue bonds due from 2022 to 2040*	$	1,153,240	$	1,010,600
Notes, 4.125%, due 2022		600,000		600,000
Notes, 4.000%, due 2023		500,000		500,000
Notes, 2.000%, due 2025		500,000		—
Notes, 3.950%, due 2028		500,000		500,000
Notes, 2.700%, due 2030		500,000		—
Notes, 6.400%, due 2037		543,331		650,000
Notes, 5.200%, due 2043		338,133		500,000
Notes, 4.400%, due 2048		329,219		500,000
Notes, 2.979%, due 2055		439,317		—
Finance lease obligations		90,338		85,224
Total long-term debt and finance lease obligations		5,493,578		4,345,824
Less premium on debt exchange		180,045		—
Less debt issuance costs		30,859		25,259
Total amounts outstanding		5,282,674		4,320,565
Less current maturities of long-term debt		—		20,000
Less current portion of finance lease obligations		10,885		9,264
Total long-term debt and finance lease obligations due after one year	$	5,271,789	$	4,291,301

Annual aggregate long-term debt maturities are: none in 2021, $601.0 million in 2022, $500.0 million in 2023, none in 2024, $500.0 million in 2025 and $3.80 billion thereafter.

In April 2018, Nucor issued $500.0 million of 3.950% Notes due 2028 and $500.0 million of 4.400% Notes due 2048. Net proceeds of the issuances were $986.1 million, of which $500.0 million was used to repay the $500.0 million of 5.85% notes that matured June 1, 2018. Costs of $11.9 million associated with the issuances have been capitalized and will be amortized over the lives of the notes.

During the second quarter of 2018, Nucor amended its $1.50 billion unsecured revolving credit facility to extend the maturity date from April 2021 to April 2023. Costs associated with the amendment were immaterial. The unsecured revolving credit facility provides up to $1.50 billion in revolving loans and allows up to $500.0 million in additional commitments at Nucor’s election in accordance with the terms set forth in the credit agreement. Up to the equivalent of $850.0 million of the credit facility is available for foreign currency loans, up to $100.0 million is available for the issuance of letters of credit and up to $500.0 million is available for the issuance of revolving loans for Nucor subsidiaries in accordance with the terms set forth in the credit agreement. The credit facility provides for a pricing grid based upon the credit rating of Nucor’s senior unsecured long-term debt and, alternatively, interest rates quoted by lenders in connection with competitive bidding. The credit facility includes customary financial and other covenants, including a limit on the ratio of funded debt to total capital of 60%, a limit on Nucor’s ability to pledge the Company’s assets and a limit on consolidations, mergers and sales of assets. As of December 31, 2020, Nucor’s funded debt to total capital ratio was 32%, and Nucor was in compliance with all covenants under the credit facility. No borrowings were outstanding under the credit facility as of December 31, 2020 and 2019.

In May 2020, Nucor issued $500.0 million of 2.000% Notes due 2025 and $500.0 million of 2.700% Notes due 2030. Net proceeds of the issuances were $989.4 million. Costs of $8.4 million associated with the issuances have been capitalized and will be amortized over the life of the notes.

In July 2020, Nucor became an obligor with respect to $162.6 million in 40-year variable-rate Green Bonds to partially fund the capital costs, in particular the expenditures associated with pollution

prevention and control including waste recycling, associated with the construction of Nucor’s plate mill located in Brandenburg, Kentucky. The net proceeds from the debt issuance are being held in a trust account pending disbursement for the construction of the facility.

In December 2020, Nucor exchanged $106.7 million of its 6.400% Notes due 2037, $161.9 million of its 5.200% Notes due 2043 and $170.8 million of its 4.400% Notes due 2048 with holders of the existing notes for $439.3 million of its 2.979% Notes due 2055 and a cash component of $180.3 million. This exchange transaction has been accounted for as a modification and, as such, the cash component of $180.3 million has been capitalized as a reduction of long-term debt and is being amortized into interest expense over the life of the new notes.

Harris Steel has credit facilities totaling approximately $19.6 million, with no outstanding borrowings at December 31, 2020 and 2019. In addition, the business of Nucor Trading S.A. is financed by uncommitted trade credit arrangements with a number of European banking institutions. As of December 31, 2020, Nucor Trading S.A. had outstanding borrowings of $57.9 million, which are presented in short-term debt in the consolidated balance sheet ($62.4 million as of December 31, 2019).